Hello everyone, I am getting into the world of electronics applied to the field of music. I have built a pre-amplifier circuit for an electret microphone controlled by a PTT that closes with GND, and I am facing the following problems:
The model of the headphones is as follows: Sennheiser GSP 302.
Attached is my schematic, thank you very much.
- I have to get the microphone too close to my mouth for it to work.
- Without pressing the PTT, when I speak excessively loud with the microphone close to my mouth, it can be heard through the speakers.
- We have tested to change R99 to 1k and R96 to 100k but it doesn't work.
The model of the headphones is as follows: Sennheiser GSP 302.
Attached is my schematic, thank you very much.
What is the DC bias of the OUT node? 0V? You are using a power MOSFET for switching, but they are act as a diode when off, so signals more than about 0.5V negative will be able to leak through to the output. You can see the body diode is actually represented in the symbol for a power MOSFET - its inevitable with a vertical current-flow device, which is standard for power MOSFETS.
Normally a JFET is used to switch like this as they don't have the body-diode that power MOSFETs have - some small signal MOSFETs also lack a body diode.
Normally a JFET is used to switch like this as they don't have the body-diode that power MOSFETs have - some small signal MOSFETs also lack a body diode.
You could try something like this:
R97 = 2.2 kohm
R98 = 100 kohm
R96 = 10 kohm
C114 = 47 pF
Replace Q1 with two MOSFETs in antiseries (sources and gates tied together, one drain to R99, the other to the output)
Actually a 2:1 analogue multiplexer or something with two JFETs, one in series and one to ground, would be better for the output switching.
R97 = 2.2 kohm
R98 = 100 kohm
R96 = 10 kohm
C114 = 47 pF
Replace Q1 with two MOSFETs in antiseries (sources and gates tied together, one drain to R99, the other to the output)
Actually a 2:1 analogue multiplexer or something with two JFETs, one in series and one to ground, would be better for the output switching.