Friday, March 19, 2021

Emitter bypass cap

 When you begin to analyze a circuit the first step is to open the caps and short the coils. Then analyze the DC paths. Establish the bias to determine the Q points.

The AC function can be seen by adding the caps and coils back in the circuit. If you build a sim with no caps and then add the AC signal you will have degenerative feedback developed across the DC bias components. Build an alternate AC signal path with the caps allow the AC impedance to be different from the DC resistance.

So remove the bypass and look at our circuit.

The circuit is functional. It produces a good signal. (faithful, linear )

Not put the bypass back in.

We get a higher gain but the signal is less faithful.

You can remove the source bypass and get the same results.

We see builders who make (regenerative) receivers with audio amps. (or so they say)

If you have a strong station in your area you could connect an antenna to the input and receive the station. Is it a regen receiver?

Consider this before answering.

As the circuit was first presented you would have some 'drain bend' which could allow it to be used as a receiver. Try adjusting the source bypass and see what happens.

Some drain bend there.
So you can change the component values and see the effects.
The simulator will present garbage in - garbage out effects but more on that latter.
I will try and present some more sim function as we go through more circuits.

For now one point to consider is the lib is built by pro's and work quite well so after you built a circuit use the select component option to ensure you are using a 'full' representation.

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