Primitive radio with an op amp?

[Resistanceisfutile]

So I was using an op amp to amplify audio, and found it started picking up radio stations.
I was just wondering... if I were add this additional circuit would I be able to build a primitive radio reciever?

(Please say if the grounds are in the wrong places)

 

[betwixt]

You would be using it to amplify the differential across the diode so it would to some extent work as a radio receiver. You would get far better results wiring it as a conventional crystal receiver the using the op-amp to amplify the audio though.

Brian.

 

[Audioguru]

The diode rectifies the AM radio transmission if it has a very high signal level more than 0.6V, so it is an AM detector. Then the opamp amplifies the audio.
You show a crystal radio driving an opamp. A crystal radio has very poor performance.
Of course the detector diode needs to be in series with a resistor so it does not short the tuned circuit and the opamp needs to be properly biased and have negative feedback. The opamp also needs input, output and feedback to ground capacitors.

 

[Audioguru]

I forgot to say that the opamp will not work because it is not powered. If it is powered, is properly biased, has negative feedback and has coupling capacitors then it does not produce enough output current to drive a speaker.

 

[Nik_2213]

Google for 'single ic radio' and pick out ZN414 and its kin, such as TA7642.

Alternative is to build a traditional 'crystal set' with LC tank and signal diode, then amplify with a micro-power op-amp.

Of course, if you are within a few kilometres of a city's powerful AM station, there are reliably documented cases of folk getting whisper-strength reception via their dental work...

More seriously, there's the 'Science Fair' trick of rectifying signal from the local mega-station to tickle a flea-powered amp and pull in national stations...

IIRC, latest take on this is to 'thieve' enough micro-Watts off-air to s_l_o_w_l_y charge up a small capacitor then pulse a tiny LED...