How to make an BJT astable multivibrator run faster than 30Khz that works?

I am working on a dc to dc converter and it works but it seems to me that when i go higher than that it doesn't work anymore. I am using two C945 transistors. The resistor values for R1 and R4 are 1K and for R2 and R3 are 15k . For the capacitors C1 is 2.2nf and 1nf for C1. i have tried putting in smaler capacitors and increasing the two base resistor values. BTW its for a dc to dc converter that im working on. I also have no idea how much inductance on the inductor is. I am try to step up 6V dc to 15 V. It works put its low on power thats what i want.

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VIRON7 years ago
30Khz? How do you know it isn't working, and how do you change it's speed? Got a O-scope? Frequency counter? AM radio? Can your meter measure high frequency voltage? If you could hear sound from it before, see if a dog notices when you turn it on because you can't hear it anymore. The circuit I'm familiar with has 2 capacitors, use smaller ones and it goes faster. 30Mhz is possible, 100Khz is easy. To test with an AM radio, put it behind the radio, and see if you get totally quiet frequencies 30Khz apart something like 1000, 1030, 1060, 1090 when it's on, maybe add a long wire for a test transmit antenna to the transistor that isn't powering the transformer or voltage doubler. If both transistors power the transformer then the problem maybe using a 50-60 Hz transformer which doesn't work at 30khz.
josh1001 (author)  VIRON7 years ago
Im using two C945 transistors and R1& R4 are 1k, R2 &R3 are 15K. the capacitor C is 2.2nf and C2 is 1nf to give me a 68% duty cycle but when i put in smaller capacitors it doesn't seem to work better. BTW im working on a dc to dc converter i don't have an oscilloscope and its the inductive type. sorry i don't have a schematic to show u.
Also, if you use a crappy socketed breadboard, you will struggle with high speed analogue circuits.
Try a Royer oscillator like the one on my site.

circuit ? Component values ? Transistor type ?