A capacitor question, ceramic versus film.

[Chris Wilson]

In the attached circuit C1 and C2 are 470pF for the MF version. I built the LF version and used polypropylene caps, easily found in 1nF value. I am building the MF version now, and I  do not have poly caps in 470pF, is there any reason not to use ceramic through hole caps there, at 470pF? Thanks.

[jmelson]

Just use NP0 caps, and it should be fine.  Most likely anything at all will also be fine, is is just 5 V signals, anyway.

Jon

[David Hess]

In almost all cases, ceramic C0G/NP0 capacitors can be used in place of film capacitors.  In many cases including this one, ceramic X7R capacitors (10% tolerance) would also work.

[pwlps]

Poly caps are much more stable (temperature, aging) than the ceramic ones so you would use them e.g. in an RC or LC oscillator, but I don't see any reason to not to replace them with ceramic caps here.

I have a question: in your circuit the high and low side mosfets are driven in quadrature (from the 7474), what is the purpose of that?

[Chris Wilson]

Thanks for the replies, I guessed the ceramics would be OK as coupling caps in this application but thought it prudent to check and be sure, I  know now for next time, and I much appreciate all the help

[Chris Wilson]

Poly caps are much more stable (temperature, aging) than the ceramic ones so you would use them e.g. in an RC or LC oscillator, but I don't see any reason to not to replace them with ceramic caps here.

I have a question: in your circuit the high and low side mosfets are driven in quadrature (from the 7474), what is the purpose of that?

I am not able to answer that, I am a relatively novice builder of it, not the designer, but if it's relevant and helps, the signal applied to the input is X2 the wanted frequency and the circuit divides by two and the output is half the input, Class D. All similar amps for LF and MF amateur bands usage seem to use the same topology. Sorry, I am not sure that really answers your question Thank you for the info re the capacitors.