0~15Mhz (0.5 ~ 2.5V pp)amplifier working from 1 ~ 65V DC supply

[tsehonkit]

Hello there,

I would like to know how to design a amplifier which can operate from 1VDC to 65VDC supply with input signal swing from 0.5V to 2.5V peak to Peak.
Output signal hope to be swing from rail to rail.

I come out a simple circuit but it just can operate up to 100K max. still not rail to rail.

Is there any idea I can improve it? I am not much experience in this area. Hope you guy can help me. Thanks.

Here is the schematic

 

[neddie]

You will need to give the output current as well.
I fear that this won't be a trivial exercise , the slew rate required is over 6000V/us.

 

[schmitt trigger]

Hello there,

Here is the schematic

Agree that the output load means everything.
If you would like to have an output load of say 50 ohm, the design would be significantly difficult.

 

[tsehonkit]

Yes, this is not a exercise, the load will be around several Kilo ohm to several Mega ohm say 300Kohm to 1Mohm. I found some material that can run mega Hz but at a fixed voltage say 30V etc. However, I need to vary the supply voltage of the output from 1V to 65V. Other circuits are run at 3.3V. So, the amplifier should as simple as possible to keep it run at a varying supply. The output drive current should no more than 300mA at 65V. Is it difficult? How far can I push it?

Thank a lot for replying!

 

[schmitt trigger]

I wish I could help you, but your requirements are too difficult and extensive for a simple, three transistor circuit.

 

[tsehonkit]

If I want to maintain output drive vary from 1V to 65V, how do I relax the requirement? I have think about multistage amplifiers and reduce the input frequency to several Mega Hz and regulate the input signal by a 74hc74 to produce a 0V to 3.3V square wave for the amplifier's input. Do you thing this is more feasible to make it? Thanks.

 

[schmitt trigger]

The most difficulty I see is in the range of supply voltages.

Below 3 volts, the output swing will become very limited when using discrete bipolar transistors.
On the other hand, at higher voltages, the power dissipation could become excessive.

And as Neddie mentioned, the slew rate is quite high. Which to increase one needs to increase the biasing current, which in turn aggravates the dissipation problem.

Why do you need such a wide range of supply voltage? Could you regulate it a narrower range?

 

[tsehonkit]

My client need to have such a wide voltage range output. Frequency range can narrow down to 0 ~ 5MHz. If I use two stages amplifier, will it be better? Using push pull output, can it improve the slew rate? But I think it will burn more current during switching. Thanks!

 

[schmitt trigger]

Wait.......... for the 1 to 65 volt requirement.

Is it the OUTPUT or is it the DC SUPPLY INPUT?

Definitively a pushpull or complementary pair will be required for the output for fast slewing.

I'm trying to find an old Tektronix note on designing ultrafast amplifiers for CRT-based oscilloscopes.

 

[tsehonkit]

The supply voltage is 65V and the output can vary from 1V to 65V. I can derive a 3.3V for the control circuits from 65V. At first, I think I can use a amplifier which can work from 1V to 65V and drive a output current drive to give a variable voltage output signal. However, the circuit I used is not good at high frequency. Or I can't find a suitable component or circuitry to do the job. Is I make fundamental mistake in designing the approach? My approach is using a micro-controller to derive different frequency for signal input and also control the output drive voltage. Many thanks for your advise!

 

[schmitt trigger]

As I mentioned, the closest to your application I can think is an osciloscope's video amp.
I used to have a note somewhere....not sure if I still have it. Last night I looked up for it briefly....let me see if I can find it.

 

[tsehonkit]

Thanks a lot, schmitt trigger.