Does this circuit have a specific name that I can look up and read about ?

It's basically a grounded-base (non-inverting), BJT amplifier, which has the novel ability to act a positive-to-negative voltage level shifter.
That configuration, with a PNP transistor, allows a positive input signal to control a negative voltage at the collector.

When the input is zero, the transistor is off, and its collector output goes to the -5V rail.
When the input is a positive voltage, the transistor turns ON with an emitter-collector current approximately equal to the input volage minus Q2's Vbe voltage divided by R1 --- Ic = (Vin-0.7V)/R1.
The output voltage is then -5V plus the R3 voltage drop of the collector current times R3 --- Vout = -5V + Ic*R3.

[These calculations assume the relative values of R1 and R3 are such that the transistor stays in the linear region (not saturated) when ON.]

I don’t want the 2.4V level to be fixed -— but instead adjustable

Post #19.

 

It's basically a grounded-base (non-inverting), BJT amplifier, which has the novel ability to act a positive-to-negative voltage level shifter.
That configuration, with a PNP transistor, allows a positive input signal to control a negative voltage at the collector.

When the input is zero, the transistor is off, and its collector output goes to the -5V rail.
When the input is a positive voltage, the transistor turns ON with an emitter-collector current approximately equal to the input volage minus Q2's Vbe voltage divided by R1 --- Ic = (Vin-0.7V)/R1.
The output voltage is then -5V plus the R3 voltage drop of the collector current times R3 --- Vout = -5V + Ic*R3.

[These calculations assume the relative values of R1 and R3 are such that the transistor stays in the linear region (not saturated) when ON.]
Post #19.

OK
So I can use the 2N5771 for 10MHz switching?

I will share my idea and my design with you.

Ultimately, I want to switch a power amplifier that is powered from a negative voltage. I don’t want it to be on all the time, but only during transmission.
Its operating voltage is a negative voltage around -2.5V. This can be adjusted, since it needs to be set to a specific bias point. When I want to turn it off, I apply -5V to it.
In one configuration, I would like to be able to switch between its operating voltage and its shutdown voltage at around 10 MHz.

There are two possible options:

1. Switch before the op-amp, configured as an inverting amplifier. In this case, I would switch between two positive voltages and then invert them to negative voltages using the inverting amplifier.
2. Feed the operating voltage (for example, +2.5V) through the inverting amplifier to generate -2.5V, and then after the inverting amplifier switch between -2.5V and an external -5V.

There may be other possible approaches, so I would be happy to hear additional suggestions.


Thank you very much.

 

Still confusing.
You say the "operating voltage" is -2.5V.
Its that a signal to a high impedance input or the power to the amp?

In one configuration, I would like to be able to switch between its operating voltage and its shutdown voltage at around 10 MHz.

What are those voltages?
Why so fast?

 

Still confusing.
You say the "operating voltage" is -2.5V.
Its that a signal to a high impedance input or the power to the amp?

What are those voltages?
Why so fast?

Hi,

The operating point (quiescent point) varies because I am working with a Power Amplifier (PA). I follow the turn-on sequence as specified in its datasheet to reach a specific current value determined by the voltage. In each component, the voltage ends up being slightly different to achieve the optimal operating point.
The "-2.5V" supply feeds the VGG pin of the power amplifier, which is a high-impedance input.
Regarding the switching frequency—I am looking into something as part of my studies, which is why I am attempting to work at this specific frequency.

Thanks a lot

 

@Toni Rodri
Why 10 MHz?