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TDA2003 opamp question? Answered

Hello i have some questions about the opamp TDA2003. 1.In the picture bellow the R1 and R2 make the gain for opamp .Gain=R2/R3=220/2.2=100. It's of if i replace the R2 with 2k resistor and R3 with 200 Ohms resistor ??? The gain still the same but i dont know if it still ok ?? 2.What the  C2(470uF) do in this schematic, what will happend if i replace it with a 100uF capacitor ? Thanks for advance! sorry for my bad English !

Question by login721    |  last reply


How to protect OpAmp output?

Hi, I have an OpAmp which controlls the Gate of a MOSFET. When the MOSFET dies, sometimes the voltage it's running on (50V) somehow gets to stand over the OpAmp's output which destroys it. What's the best way to protect the OpAmp from the high voltages that get to stand over the output? Will a zener do the trick? Trigger transformer won't be easy to use here because It's a PWM controller so I need nice block waves. Diode on the output? but won't this be bad for delivering good current to the Gate? ... Any ideas?

Question by DELETED_Electorials    |  last reply


opamp voltage bias question.? Answered

Hello. i have a question about voltage bias.In some schematic of opamp use single power source , they use R1=R2 to make voltage bias (please see the example bellow) . But the value of R1 and R2 in other schematic i found are diffirent (R1=R2=100k or R1=R2=47k ,.... etc) How did they effect the circuit ? Thanks for advance ! sorry for my bad English .

Question by login721    |  last reply


Wanted: OpAmp IC's (those with 8 pins and two OpAmps inside)

Hello, Would it be possible for someone to send me some OpAmp IC's (8-pin DIP) with two OpAmps inside? (for free? :) ) They don't have to be power OpAmps, but just regular OpAmps with a Vccmax of at least 20V. I need them for some PWM projects I have. If you are interested or if you want some more information, please send me a PM :) Thanks in advance, Electorials

Topic by DELETED_Electorials  


Need help with DC bias of opamp Answered

Hello .I want to make a simple headphone amp with active mixer ,use single power supply. The first schematic is combine of simple opamp mixer and cmoy headphone amp,and its work fine.But can i want to reduce the board size.so can i remove a resistor(schematic2) and a capacitor (schematic3)  ? Thanks for advance! sorry for my bad English.

Question by login721    |  last reply


non-inverting opamp gain question?

Hello. i have a question about non-inverting opamp gain .In the image bellow ,the resistors make gain =1k/220=4.5.4 Now i need to turn the gain down ,but i only can change the value of 1k resistor.It's ok to lower the value of 1k resistor ,or even remove it ? http://i247.photobucket.com/albums/gg132/chipmapple/opampgain.png Thanks in advance!

Question by login721  


Question about opamp, resistor and capacitor? Answered

Hello i have some questions. 1.Im going to build a ROG Tonemender (http://www.runoffgroove.com/tonemender.html).What the 10M resistor do in this schematic ? and its ok if i use a smaller value like 2M or 4M7 ?? 2.If a opamp rated output 10W with 4 Ohms speaker, how many W i can get if i connect it with a 8 Ohms speaker ?? can i have the formula for this please. 3.My amp have output power is 100W , can i connect a 8 Ohms 26W speaker to the amp ? 4.I want to find an opamp like LM386 but use lower supply voltage (5v) can you give me some suggest please. 5.What type of capacitor in the picture bellow ? Thanks for advance. sorry for my bad English!

Question by login721    |  last reply


What software can i use to draw graphic analysis frequency response of opamp circuit? Answered

 I'm finding a program can draw the graphic analysis frequency response of opamp circuit from schematic (some thing like the image below) . What program can i use to do it ?Can you tell me please ! Thanks for advice! sorry for my bad English!

Question by login721    |  last reply


i want to make a project based on ic 741 or ic 555 . please help?

As a part of my college projects, i want to a project based on ic 741 or ic555..

Question    |  last reply


Can't get a TLC272IP OP-AMP to work. what am I doing wrong? Answered

Hello I received this week a few TLC272IP op-amp and I wanted to test them. I created a circuit on a breadboard which looks like the attached image From what I read on the net, this is a  typical non inverting amplifier schema where gain should be (1 + R2/R1) I connected PIN 3 of the TLC272 to pin 3 of my arduino uno and using PWM I set the output to roughly 1V ("analogWrite(3, 51);") I used my voltmeter to read the voltage between ground and pin 3 and I could really see 1V  given I used R1 = R2 = 47k, I was expecting to have a gain of x2 and thus read voltage of 2V between pin 1 of the op-amp and ground  I get something that is very unstable, below 1V. I tried with 4 different TLC272IP I just got and get the same behavior. am I doing something wrong there? what do I miss? or do I need to review how op-amp are really working? (I purchased the TLC272IP because it's supposedly single power supply) thanks for any hint. JM PS. in some doc i read that I should not let the second op-amp in the air, so i tried as well by connecting pin 5 to ground and shorting 6 and 7 with a wire or a small 100k resistor but this did not change anything.

Question by jm-l    |  last reply


How to power an opamp(with -5v) form USB?

I`m making a dac+amp with usb input and headphone out. I`m powering it from USB. The USB controller and the DAC uses 5v and 3.3V, but the opamp(LM4562) uses +-5v. How could I get this differential voltage form the 5V of the USB, even if i get less current. If you can give me a good IC, it would be great, but if you can give me even a schematic (+IC) would be awesome.

Question by fmada    |  last reply


Need help with caculate non inverting op amp gain? Answered

Hello .I need help with caculate gain of this non-inverting opamp .Can you tell me how to caculate the gain of it when the pot at 100% please ! Thanks ! Sorry for my bad English!

Question by login721    |  last reply


Building a current booster circuit

Need to understand whats going on in this circuit which is a class project.

Question by ighalo_joshua    |  last reply


Can someone make a breadboard layout for this schematic? Answered

I already have a pulse detector module.. simple with LED and photodector.. It has 3 pins: VCC, GND and one ouput(from photodetector) as signal.. I want to amplify the signal using op amp LM324 i have the following resistors available: 10Ω、22Ω、47Ω、100Ω、150Ω、200Ω、220Ω、270Ω、330Ω、 470Ω、510Ω、680Ω、1KΩ、2KΩ、2.2KΩ、3.3KΩ、4.7KΩ、 5.1KΩ、6.8KΩ、10KΩ、20KΩ、47KΩ、51KΩ、68KΩ、100KΩ、 220KΩ、300KΩ、470KΩ、680KΩ、1M and following capacitors 50V 2.2UF 100V 10UF 50V 10UF 16V 100UF 16V 47UF 25V 33UF 50V 1UF 16V 220UF 50V 0.22UF 50V 4.7UF 50V 0.47UF 25V 22UF

Question by Rahul27    |  last reply


Amplify 1.5v DC to 5+v DC?

Hi, Anyone know if I can amplify 1.5v DC to 5+v DC (pretty much any value over 5 works) using the LM358 IC (https://www.sparkfun.com/products/9456)? The datasheet (http://www.sparkfun.com/datasheets/Components/General/LM358.pdf) specifies the power supply range as 3V to 32V however the input voltage range is -0.3V to 32V (top of datasheet page 2). I've done some googling but I'm still not sure about the difference between these two.  Any tips or links on wiring this guy up would be awesome, Thanks!

Topic by sciguy77    |  last reply


Input problem with OpAmp-controlled ZVS Induction Heater

Hello, Idea: I'm trying to build a circuit which uses an OpAmp to drive 2 mosfets, which power the LC tank of an induction heater. The idea is to detect when the voltage over the LC tank crosses zero, and at that voltage I would make the 2 outputs of the OpAmp change states from fully on, to fully off. The two OpAmps (both inside one chip) have their positive and negative inputs connected to eachother, but with reversed polarity. This would make sure that one output is high, and the other one is low. Why use an OpAmp? I wanted the MOSFET gate switching to go faster as usually, because in the mazzilli circuit, the gate voltage actually slews at the same rate as the LC tank's voltage slews when it crosses zero volts. In the mazzilli circuit, it actually doesn't switch when the voltage is 0v, but when the tank voltage drops below the gate threshold voltage. This would mean that you are always switching current at 5v (for example) instead of at 0V. So for these two reasons, I wanted to try switching them with an OpAmp. Measurements: Probe I on drain 1, probe II on drain 2, and GND on the circuit's ground, gives me an expected result: when switching states, at 0 voltage of the LC tank, the voltage on one side stays low (since it's pulled to ground) and the voltage on the other side goes from 0v up to 50v, back down to 0v, like a sine-wave. Then the OpAmps switch again, and the one side now goes up to 50v as a sine wave, and the other one stays low at 0v. All good, this is working just fine. Probe I on the one differential input line, probe II on the other differential input line. Since this is nothing more than just a 1/10 voltage division of the previous measurement, I'm also expecting the signal to be exactly the same, but 11x smaller. -> problem: However, this does not happen. Because of some strange reason, as you can see in the scope images: Both channels go high, Twice per cycle, instead of going high only once per cycle, and staying low for the next half of the cycle. This really isn't good! Do the inputs affect the waveform in some way? Remarks about scope images: Image: 2 gates Blue gate voltage seems 'quite' fine. Turning on looks good, turning off is not really good becuse if tends to turn on for a short time once again, before it fully turns off. Yellow gate voltage is terrible. Turning on doesn't happen as expected. Voltage drops back to 0 for a long while which is very bad for the circuit. Frequency seems fine; 50kHz is as expected with the 14µH and 6µF. Image: 2 drain voltages These voltages were measured with a 1-10 voltage divider, and thus show only 1/11th of the actual voltage. This is getting close to what I want the LC tank to do. The voltages seem quite like sine waves. I suspect that if the gate voltages would be as they should be, these drain voltages would also be perfect sine waves. The regular sine amplitude of 50V is as expected, with a 24V supply voltage, but at the moments when the drain voltages strangely drop down to 0v, as you can see in image: '2 gates', at these moments the drain voltage seems to spike over 250V!! Image: 2 differential input lines This is the image which I don't understand. I expect the same wave as in the previous picture, but only 11 times smaller because of the voltage divider. However, the voltage does NOT reach 0v while the drain voltage does, and its shape is also completely different. In this image, both channels are doing one (half) sine wave, twice per switching period. They should be LOW for half a period, as the drain voltages do in the previous image. Better quality images: 2 gates 2 drain voltages 2 differential input lines schematic Datasheets: OpAmp: http://cds.linear.com/docs/en/datasheet/1497f.pdf MOSFETS: http://www.vishay.com/docs/91262/91262.pdf Coils and capacitors: Line inductor value: I'm not sure if this value is correct. Center-tapped main coil inductance: This value should be pretty correct, I calculated it by measuring it's size and windings, and the operating frequency is also nearly the same as the calculated one. tank capacitance: 6 times a 1µf MKP capacitor Questions: - Why these strange large spikes? - Why is the waveform suddenly different when reading it near the differential inputs? For the first time ever, I can provide you with scope images! I finally bought a (quite cheap) oscilloscope. I hope it helps a lot. Oh, and one more thing: The induction heater does actually work already. I'm getting huge currents in the LC tank, since the 6mm copper tubing gets hot after a minute. Water cooling has been added, and it works like a charm! The MOSFETS do get quite hot after 15 seconds of heating an object, or after 40 seconds of heating nothing. This, probably because the gate voltage isn't what it should be. Kind regards, Electorials

Question by DELETED_Electorials    |  last reply


Question about op amp frequency response? Answered

Hello , i have some question about op amp frequency response. i use non inverting like the scematic below.If i set  R1=10kΩ  , C1=220nF  ,  R2=100Ω  , C2=1uF . R1 and C1 will set low frequency response of opamp at 72Hz . R2 and C2 will set high frequency response of opamp at 1592Hz.  But how much it affect the signal in dB ? and how its affect the signal if i set R2=100k ,C2=1n (gain~11)? Can you give me the formula please ? Thanks very much! Sorry for my bad English!

Question by login721    |  last reply


Operational Amplifier input voltage affects other input?

Hello, I have created a simple circuit where 2 10k resistors make a voltage divider. Supply voltage is 12.5V and if I measure in between the 2 resistors, I'm getting 6.3V. Great! Now I connect that 6.3V to the +input of an OpAmp. Result: the value is still 6.3V. Great! (The OpAmp is also fed with 12.5V) Now I connect the -input of the OpAmp to the supply voltage (12.5V). The voltage in between both resistors suddenly changes from 6.3V to 10.1V. NOT Great! Now I connect the -input of the OpAmp to ground (0V). The voltage in between both resistors changes from 6.3V to 2.4V. ?! The output of the OpAmp is not connected to anything. I thought that OpAmp inputs, in theory, have infinite resistance? The datasheet of this OpAmp (LT1253) sais the input resistance should be 10Mohm I also tested this same thing with the LT1497 and the results are the same. When the -input of the  OpAmp was connected to 12.5V, I measured the current going into that pin, 39mA!! (Only measured on the LT1253) What's the problem here? Are both OpAmps broken? Or is there something about the way OpAmps work, that I clearly don't understand?

Question by DELETED_Electorials    |  last reply


Can I use 741 op amps instead of 1 LM324 in a heart rate sensor?

Http://makezine.com/video/visualize-your-heartbeat-with-this-homemade-pulse-sensor/

Question by DangerousTim    |  last reply


Comparator Inputs ?

On the two inputs of a standard comparator op amp (say for example  LM741)  they usually  connect resistors from both the positive and negative voltage rails .Why do they do this and how does this work . This has been on my mind for a really long time . Could someone give me a really detailed explanation maybe with images if possible , cause this would be really helpful in the building of my next project .Most of the tutorial videos out there , i don't understand either. Thank you in advance  

Question by Strontium    |  last reply


DC Motor Burning Issues? Answered

I connected 6 Volt 4.5 AH Battery to a motor directly and that burning electronic smell came. Should i limit the current? If so, Then how?

Question by yhdesai    |  last reply


Help on a divide and blend circuit - wet and dry - tl072

Hello,i want to build a "divide and blend" circuit with one potentiometer to blend between a dry and wet signal, the source will only be audio and the wet signal will be a clone of the MS-20 filter.my knowledge of electronic is almost zero... so i looked on different circuits and tried to adapt to what i want, but i need you guys to confirm if what i've designed works? do you see any problem? to you have any suggestions? thank you very much

Question by FilipeB21    |  last reply


Problems with logic(NAND) gates? Answered

I MADE a circuit that basically detects when an IR beam  is cut using a LM741 opamp .AS shown in the schematic i've connected the output of the opamp to the  two transistors (which is a nand gate) ,so when the beam is cut the output of the transistors should be high but instead the led at the collecter of the transistor glows only brighter. should i use a nand gate in a DIP package ?also when i individually measured the output of the opamp it showed that there was constantly 1.5 v coming out i tried measuring it with both opposite polarity leads of the multimeter  ,still  it showed a 1.5 v output,why does this  happen?PLS help.i need it fast.

Question by Strontium    |  last reply


DC offset volatage

How do I provide a 5v dc offset volatge to a sine wave? (Using op ams)

Question by wjayashan1997    |  last reply



Operational Amplifier not working? Answered

Hello, I'm trying to use the KA324 IC (which consists of four opamps) for amplifying an audio signal. I've tried almost every schematic from this website: http://sound.westhost.com/dwopa.htm and also from lots of other websites, but none of them work. If the output volume is Really low, the sound is pretty good, but very quiet. When I turn up the volume, the sound is really bad, I almost can't recognise the song I'm playing. The output volume is also not that really high. If I keep increasing the input voltage, the output stops increasing after a while. It's not really 'loud' at that moment too. I've connected the IC to 12V DC (between the two middle pins). The + input goes to the ground connection, the - input goes to my POT voltage divider of the input voltage. The output pin goes straight to the speaker. I also added a 100kOhm resistor between output and - input. Without that resistor, I hear nothing at all but I think that's normal. I've also tried the three other op-amps from that IC but no luck. Is this opamp just not ment for audio amplification? or am I doing something wrong? Greetings, Electorials

Question by DELETED_Electorials    |  last reply


In what electrical objects can I find op amps? Answered

Hello again, I'm searching for good op amps. They don't have to be power op amps, but it would be nice if it also had some protection circuits like a current limiter. It needs to take at least 25V differential between the negative and positive supply voltage. It should be a chip with at least two op amps inside it. Are there any broken electrical items that have these inside? I know they are 'used a lot' but somehow I don't find them often. Greetings, Electorials

Question by DELETED_Electorials    |  last reply


I need OP-AMPS Answered

I am having a hard time obtaining old op-amps (max420cpa, ltc1150, etc). Maxim/Newark/(ebay -only seldom) no longer carry them. Where can I get them at a  REASONABLE  price? Thank You. Ed.

Question by edwianni1    |  last reply


Has anyone experimented with neodymium magnets as pole pieces in a single coil guitar pickup?

I have done some modification on pickups and preamps using opamps to amplify the signal. Since neodymium magnets are more powerfull than what they normally put in pickups I wonder what kind of sound would be generated?

Question by sn3102    |  last reply


Fluctuating voltage?

I am trying to build an ammeter using a 100:5A CT and a pic16F716 and display the value using 7segments. However, The voltage I get from the CT after rectifying it using an OPAMP still fluctuates between 4.8 and 5.4 .  I don't understand what is causing it to fluctuate that way. I will attach a picture of the circuit I am working on.

Question by IndiraK2    |  last reply


Simplest way to combine a mono and a stereo source to play through a set of stereo headphones?

Ok, what I am specifically wanting to doing is make the Xbox voice chat (mono) and the game audio (stereo) come out through the same set of headphones. I quickly found out that I couldn't just wire them directly without turning the game audio to mono (not good for online multiplayer). I found a discussion about using an "opamp" and taking the mono signal and feeding it into the right channel then take the opamp output and feeding that back into the left channel to get a "stereo" output. Unfortunetly, I got as many details from that as I just gave here. Can anyone explain how and what parts it would take to do this? I also got the impression it might be passive, and no batteries would be a plus. Preferably, I would like to be able to get the stuff at Radioshack, and ideally, I would want to try and stuff the parts inside the over-the-ear cup style headphones directly.

Question by vphreeze    |  last reply


LDR or optical reflective sensor?

I am planing to make a line following robot without micro controllers. So I am using a light sensor connected to an AND GATE (the other input being the current to the motor). So since I am using" an and "gate I want the input current to be an absolute zero or some value ,ie the current should not be varrying with the light intensity. Besides I think I might drop the "and gate" thing and use an OPAMP instead as it would give me a varrying output current which is all I need

Question by chrissunny94    |  last reply


how to make a guitar tone stack?

Im making my own amp, but it occurred to me that i'll need gain, bass, mid, and treble controls as well. i know these are generally part of the preamp but i cant seem to find one that is simple, with few parts (small opamp , 4 or 5 pots and some caps/resistors). oh yeah if you could show me a site that carries all the part too thatd be nice, becauseive always used all electronics, but thay seem to be lacking... they dont even carry a 250k pot!

Question by tigerdog330    |  last reply


How to generate a fixed differential voltage dependant on a voltage relative to ground?

What methods can I use to generate an accurate & precise variable differential voltage that's dependant on the output of a +-10V DAC? I tried to use a resistor with a small variable current sink using the classic opamp+NPN design, but no design I made would sink current below 1V. I need it to continue sinking current down to 0V, I do have a negative supply rail avalible. (I think my last question was a bit TL;DR for some, so this is a shortened version of that.)

Question by -max-    |  last reply


Jameco's newest Puzzler

Ok guys n gals, I felt good enough this morning to wade through my email, and I found the latest Jameco Puzzler, just waiting for me. I puzzled over this for about 3 minutes, and then guessed and low and behold.......(see the figure below) So anyways, HERE is the puzzler, make a guess before looking at the answer :-)This is NOT a contest, have fun with it....for those that have electronics background, think about it for a bit, remember how an opamp works, and you should be able to get it right on the first guess. Above all though, have fun with it.

Topic by Goodhart    |  last reply


Converting 12v DC to 5v DC

Greetings, I’m very new in electronics. I would like to connect my analog camera that uses 5v dc to my car battery. So I need your help to make a voltage converter. From what I have understand searching the web, I will be possible and very easy actually. All I would need is an opamp and some resistors?!!! Right? So any diagram or anything that you can help me with will be more than appreciated. Thank you for your time reading this. Best Regards P.S. I hope I’m in the right place writing this topic  

Topic by toqilula    |  last reply


Grounding a magnetic levitation circuit

I need help understanding the circuit attached, from what i understand is that i can power it from a 12V mains adapter. The one i have is 1 amp which i think is enough. But more importantly for the grounds, that i should connect them all up to the ground coming from the 6 pin on the left opamp. As though this ground would act as a central one, with all the other ones connected to it. Is this correct or not, if not then please explain to me how i should ground this circuit. I claim no rights to the content in the link and am using it for my own recreational purposes. http://uzzors2k.4hv.org/projectfiles/magneticlevitator/Magnetic%20Levitator%20circuit.GIF

Topic by o0SLOVAKIA0o    |  last reply


7805 and 555 timer circuit heat.

Hi all! I made a test led blink circuit with a 555 timer on a bread board. Just a basic two led blink circuit you can find all over the place. I used a 7805 for a supply regulator with power from a 9v batt. The circuit functioned fine (to my knowledge), but the 7805 got REALLY hot. I've used 7805 in opamp circuits with a 7.2v batt and no detectable heat. Is what I'm experiencing normal? Or do you believe something I did was wrong. If I remember correctly (I'm really tired as I write this) i was using 100nf caps on both ends. Thank you Nic

Topic by Mrlzeppelin    |  last reply


I need to build a light sensing circuit for a class project.

Hi, I need to build a light sensing circuit for a class project. I have already built one circuit using a 741 opAmp chip, a 1 meg ohm photo cell, a 1 meg trimmer, a 1k, 100k, and a 47 ohm resister, and a 2n2222 transistor  as well as a 12vdc relay.  The circuit senses the light and the sensitivity can be adjusted by the potentiometer.  It works great for tuning it in to need a certain amount of light intensity to trigger the relay. The problem is i need to be able to put limiting factors on it.  I need to be able to set it to turn the relay on if a certain intensity is reached, but not turn on if the intensity gets to great.  Is there anyone who can help me with the schematics on how to achieve this?

Question by bambam1.61803399    |  last reply


Simple PIR circuit, need review

Hi, I'm working on a simple circuit. The idea is to have a portable device that lights up when I stand up at night. I have a PIR sensor that triggers 3 LEDS. I use a LM741 as an OpAmp The leds are type 3528. Though these LEDs are supposed to be powered with 12v, I'll use a 9v battery. My main concern is the battery life, tha'ts why I use 100k resistors in stand-by, to limit the current. R3 is used to fine-tune the threshold on the inverting voltage. PIR outputs:    3.3v when it detects motion,    ?v otherwise (but yet >0) Could anyone give me some tips or advice on how to improve my circuit? Thanks, Antonio

Topic by stills    |  last reply


Quadcopter without expensive ESC?

Well I am new to quadcopters so please forgive me if I am wrong. Well I am set about to build a quadcopter and was doing a bit of research on the internet and most of them were telling me to get ESC for controlling the speed of the motor. I want to know if I can substitute it with something cheaper which basically varies the output using pwm input from the microcontroller(something like opamp) Another question is about motors ,is it a must that I should get brush less motors We'll I have two options Brush less 1500Kv motor for about 30$ each Normal 24000rpm 12v motor for 6$ each So which one is better and if brushless why so. Apart from that how much would a completely finished quadcopter wiegh (approx weight)

Question by chrissunny94    |  last reply


op amp as comparator basics? Answered

Well... I'm making this battery charger cum level indicator, which should turn off the battery supply when its voltage drops below 10V. Im using an opamp as a comparator to do that. I have been scratching my head for 3 days but cant get this sorted. From what I have been experiencing for years, on an op amp if the potential on the in+ pin is higher than that on the in- pin, then the output pin goes high, else low. Right?  Now in this particular case (and the first time in my life) the ic gives 4.xx Volts on the output pin when in+ is higher than in- and 11.xx volts when in- is higher. Vcc is 12V.  Im bugged... I have attached the part of the Schematic that shows the IC and its connections. Please have a look. I haven't changed the IC yet, im doing that in a minute anyway. I'll mark this solved if the new IC does the trick. :)

Question by pro2xy    |  last reply


analog circuit to mimic constant resistance load? Answered

I unfortunately do not have many big resistors that can dissipate lots of power, and would like to make a dummy load to test and parameterize batteries and power supplies. I want constant power, constant current, and constant resistance load, I do have lots of opamps and a few N and P channel enhancement mode MOSFETs as well as many 2N3055s and a couple MJE2955's. I think constant current is the easiest, since all I need to do is make a closed loop controller that will turn off the transistor as the current is exceeded, and turn it on as the current falls. Constant power might be more tricky, as I need a device that controls the bias on a transistor as a function of the product of the voltage and current, since P=IE or W=AV, and similarly, constant resistance, I need a thing that will divide voltage across the pass element by the current through it. I don't want to use a "slow" microcontroller for this, I like nice continuous analog control system, if that is possible.

Question by -max-    |  last reply


Op amps? Which one is best?

I have a couple op amps collected over a couple years, and I am working on a design for a linear power supply, but have stability issues, and a "down to -V" common mode input voltage for op amps is a difficult parameter to find. Constraints: * Inputs must work down to as close to the negative supply rail as possible  * needs to be stable when used in a feedback loop for a linear power supply design * low noise / offset / blah blah good good goodies?? Hopefully? I'm actively testing these in a basic comparator circuit to see how far I can get the inputs to the -vee (or ground) before the op amp stops working as intended.I have tested the LM324, LM386, UA1458TC, LM741, and a few of the LT one's. Only the first 2 work well on a single supply w/ the inputs near ground or Vee LM324; // slow LM224; // ditto, but in weird thicc package LM386; // slow LM741; // ancient relics of the past, not rail to rail by any means, sucks IMO. UA1458TC // ancient relics of the past, not rail to rail by any means, sucks IMO. LM318H; // it's in a fancy metal case :D TL072CP; // JFET inputs, limited output current and the output can't go below the noninverting input. TL2072AC; // ditto. OP37; // These things aren't even that fast and can't work at unity gain. OP27; // ditto LT1007; LT1167; LT1191; LT1363; CRAZY fast, 1000V/uS!!! Maybe too fast... LT1360; LT1112;

Question by -max-    |  last reply