Two Buffer / Follower circuits

[Gus]

Two follower circuits

IMO this type textbook circuit uses the "strengths" of a N channel JFET and NPN





AND a Piezo follower



Have fun

[Gus]

I thought the people who use piezos and/or want high input resistance circuits would like this thread.

The JFET NPN circuit is another textbook circuit that seems to be ignored in effect circuits.   The JFET operates at a lower Id and the NPN supplies most of the current.

If I used just a resistive drive with the passive guitar sim  the graph would look different

The piezo one can use a voltage divider capacitor to keep the buffer from clipping if needed.  C2 keeps DC from the piezo pickup

[Gus]

An adjustment for the passive guitar/ bass follower

[Gus]

No responses?

The peak is caused by the pickup sim
The piezo is flat

[iq01221]

  I just don't get that transistors here. But, anyway, I'm looking it... I still can't see it,¿ it's made for acoustic or electric guitars?¿ Is it a cab sim( the passive one)?

[Gus]

The first circuit is a buffer just under a gain of 1 with a 1meg input resistance.  The 1 meg can be changed with different values for R5.  I have a simple sim of a one pickup guitar and cable in the sim that is why the high end peak.  The current in the JFET is low and most of the current is handled by the NPN .  This gives a source follower (SF) input and emitter follower (EF) output.

The second is a circuit with 10 meg input resistance for piezos gain just under 1, input resistance can be changed with R5.  C5 is the piezo( I guessed the value) and C4 forms a capacitive voltage divider "pad" to reduce the input to the circuit if needed.  Adjust C4 value as needed.

The last sim shows a low pass filter added and the different curves are different values of C5