Radiofrequency amplifier.

Jon, Perhaps using the Wilson Current Mirror for the output stage is a solution. It has good linearity if you use matched transistors like the lm394, etc.. Just parallel enough of them to drive 50 ohms at

Good luck and let me know what happens.

What are the requirements to linearity and gain flatness?

You betcha. This schematics has severe problems with stability. Especially if you are planning on driving 50 Ohm cables.

Only if the parasitics is accounted for.

No it won't.

Avoid general feedback. I would use a common gate FET cascade as the output stage.

Vladimir Vassilevsky DSP and Mixed Signal Consultant

Is this 50 Ohm load always there during normal operation?

If you always have the 50 Ohm loading, then the output impedance can be always above 50 Ohms and reflections won't be a problem. You can drive the load directly from the collector / drain with no need for feedback from that node.

Is this 2 cm^2 connected to a big heatsink?

Can you have any supply voltages you want?

How big of an input signal can you get?

Can you stand distortion?

Consider something like the LT1939 doing this:

!+\\ ! >---!--->!--- !-/

The diodes can provide good isolation when the two drivers are shifted to back bias both diodes.

That looks like an oscillator to me.

o a

I don't understand how a current mirror is going to work. I need the common emitter outputs because they allow me to make the output impedance go high. Also, a push-pull amp is necessary for that reason and heat reduction.

o a

I need the common emitter BJT's so that the amp has low enough output capacitance when off.

o a

There can be loads of different impedance attached to the device. I plan on using some kind of programmable back termination. Probably using a 10 ohm resistor and then a variable amount of positive feedback with a digital pot. I've left this out of the circuit as it is an extra complication.

Yes, but there are going to be 16 of these amplifiers attached to it.

as big as an opamp can make. signal is coming from an adc.

i would like to make pretty clean triangle waves as 2 mhz and a sqaure wave at 30mhz.

I'd say skip the entire "designing your own" thing and just specify an opamp with output disable function. Start here

You probably won't find one that easily meets your drive spec though.

nto a

At 100MHz, you are likely to have a lot of trouble making such a circuit be mostly real impedance. The reactive component will reflect.

With a 50 Ohm constant load I was going to suggest making the driver a constant current source.

Water cooling or do we not count the fins?

This is with a class B output stage. With class A the situation will be worse.

Can the DC-DC be shared?

Since my signals are really only 30mhz. The power at the harmonics should be kind of low. As long as I can absorb a decent amount of reflected power, all is well.

Some sort of class C or class AB is going to be the only option. There will end up being some limit on the number of outputs that are simultaneously driving some amount of current because of thermal limits. Keep Q low is going to be very important.

Yes

Sounds like fun. Some 25 years ago i was building a pulse amplifier that would deliver 10 v/v with 50 v into 50 ohms with 3 ns edges and flat tops. The proof of design unit proved the design, but the project got killed. I only needed another couple of weeks and a lot more not cheap (about $3 each) transistors. No "high z mode" possible in the design, but open circuit and short circuit safe (at least for a few seconds).