0
\$\begingroup\$

enter image description here

enter image description here

I simulated a radio-receiver circuit, where I have actually build a part of the circuit which helps to amplify a AM carrier 550 kHz frequency of microvolts (antenna voltage) into several volts, however, I do not see any amplification on the output voltage as highlighted above. I am not sure what have I done wrong. I have attached my LTspice file at google drive here for edit and just click on download and if possible, edit and simulate it in LTspice to prove that there is amplification.

\$\endgroup\$
2
  • \$\begingroup\$ You could draw the schematic a little bit more readable. Otherwise, you're lucky for the default Rser=1m for theinductor, otherwise you'd be getting voltage loop errors. Also, L1, C1 are absolutely useless here (they're in parallel with a voltage source, which has zero internal resistance). If you meant to simulate an antenna then a current source would have been better. \$\endgroup\$
    – a concerned citizen
    Oct 7, 2022 at 18:46
  • \$\begingroup\$ youtu.be/CJi93dBBUJ0 Here's an AM radio I built on a breadboard. I believe this schematic has a number of issues. In the book I told you about, there's a very similar design (also based on the LM386) without those issues, plus you don't need a special germanium diode in the book design, but only a simple silicon one. You could choose a different book of course, but in general I'd recommend a book over internet schematics. \$\endgroup\$
    – ee_student
    Oct 29, 2022 at 9:39

1 Answer 1

Reset to default
2
\$\begingroup\$

You need a resistor from the output of D1 to ground for the demodulator to work.

A value of 10k or so is a reasonable starting point.

Th resistor is necessary or the node from the diode will just charge up to the max voltage of the RF then stay there. (It may even have difficulty simulating Spice often doesn't like nodes without a DC path to ground).

C2 is rather large to get a reasonable audio bandwidth - 1000pF would be better.

In your simulation you should couple the voltage generator B1 loosely to the inductor. That loose coupling could be a small capacitor, maybe 10pF.

\$\endgroup\$
1
  • \$\begingroup\$ To better simulate the AA119, which is a germanium diode, one could put a resistance in parallel with it. Per the data sheet, somewhere around \$200\mathrm k \Omega\$ to \$1 \mathrm M \Omega\$ may be about right. Or use a Shottkey, or find a SPICE model of a germanium diode. \$\endgroup\$
    – TimWescott
    Oct 7, 2022 at 23:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.