Hi,

I am currently working with a power amplifier that I occasionally operate in a switching configuration (ON/OFF). The amplifier requires both positive and negative supply rails.

I am generating the negative bias voltage using an operational amplifier in an inverting configuration. I would like to implement a "MUTE" function so the amplifier is not active at all times. Specifically, I want to supply approximately -2.4V when the amplifier is operational (ON) and -5V when I want it to be disabled (MUTE).

This is the circuit design I am considering for the implementation :


I have two questions regarding this setup:

1. High-Speed Switching : I am looking to use a transistor as a switch for this application, with a minimum switching frequency requirement of 10MHz. Do you have any recommended components or specific transistors that can reliably handle this speed?
2. Circuit Topology: Is my current approach (using an inverting op-amp to toggle between these two negative voltages) the most effective method, or is there a better industry standard for achieving this?

Thank you very much for your assistance

 

It takes a very high-speed op amp to toggle at 10MHz with fast rise and fall times.
What is the nature of the load your are driving at the op amp output and why do you need such a high speed?

 

Is the TS intending to drive an opamp with a switched 10 MHZ pulse train??? THAT will require an opamp with about 100 MHZ frequency response.

 

Is the TS intending to drive an opamp with a switched 10 MHZ pulse train??? THAT will require an opamp with about 100 MHZ frequency response.

So what can I do? if I can switch the voltages after the op-amp but then I need to switch negative voltages and I didn't find device for this

 

It takes a very high-speed op amp to toggle at 10MHz with fast rise and fall times.
What is the nature of the load your are driving at the op amp output and why do you need such a high speed?

Hi, I’m transmitting through a power amplifier, sometimes in pulses, so I need switching. What I’m driving is the VGG pin of the amplifier with a negative voltage.

Through this switching, I control whether I turn the amplifier off or on.

 

A COMPARATOR is usually faster than an opamp. Of course a comparator is also non-linear.
What will probably help a whole lot is to provide a more detailed description of what the TS is intending to achieve.
Presently we have no hint about the overall plan.

This seems like another case of not giving out enough infoormation for any to produce a useful solution.

One possible choice would be to control the signal input to the amplifier, instead of controlling the amplifier itself.
This is often done in radio transmitters .

 

A COMPARATOR is usually faster than an opamp. Of course a comparator is also non-linear.
What will probably help a whole lot is to provide a more detailed description of what the TS is intending to achieve.
Presently we have no hint about the overall plan.

This seems like another case of not giving out enough infoormation for any to produce a useful solution.

One possible choice would be to control the signal input to the amplifier, instead of controlling the amplifier itself.
This is often done in radio transmitters .

Hi,

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.

 

OK, IF the amplifier is operating in "Class C" conditions, then it is effectively "off"when there is no input signal. That would mean no need to switch it off and on.
Going back and reading post #1, it does not make any sense to me at all. What frequency range is being amplified that it would be switched on and off that rapidly?? IT seems more like a RADAR application, which is outside of my experience realm.