Put a 10k from base to ground, emitter to ground and then apply a signal though a 10k resistor to collector.
Raise signal level till there is a spike on the scope. Scope is connected across 10k signal resistor.
I'm thinking 20v p-p with common transistors.
Raise signal level till there is a spike on the scope. Scope is connected across 10k signal resistor.
I'm thinking 20v p-p with common transistors.
When you connect a resistor from base to ground, the transistor goes into reverse conduction as soon as the collector voltage goes below about -0.6 V.
In my design I pull the base of the 2SD2704K transistor to 3,3V with a BC856B. In the past I used a 270 Ohm resistor (R1) in series to get 9mA of Ib and I have a 10k resistor (R2) to -12V.
In a current design the 3.3V rail and the -12V rail are pretty noisy that's why I thought about changing R1 to 499 Ohm to have at least 5mA of Ib and I wasn't sure about the resistor value for R2.
I use a TC7660S to generate the -12V and it is switching at a frequency of about 18kHz that is coupling into the analog signal and the TC7660S doesn't provide so much current so that it would be better to reduce the current consumption on the -12V rail.
My own experiences so far were:
In a current design the 3.3V rail and the -12V rail are pretty noisy that's why I thought about changing R1 to 499 Ohm to have at least 5mA of Ib and I wasn't sure about the resistor value for R2.
I use a TC7660S to generate the -12V and it is switching at a frequency of about 18kHz that is coupling into the analog signal and the TC7660S doesn't provide so much current so that it would be better to reduce the current consumption on the -12V rail.
My own experiences so far were:
- Using the 2SD2704K as a mute transistor the resistor value of the resistor across the signal line doesn't have to be higher than 1k2 otherwize it will worsen your THD+N. It is better to use lower values.
- something that isn't new: one mute transistor isn't enough two in a row separated by a second resistor are much better.