h-bridge and large motors

Well, first of all driving an H-Bridge with an h-brigde seems like a poor choice. For high current go with an H-Bridge made from two p-channel and 2 n-channel high current MOSFET transistors. There are a ton of schematics for this layout, and FETs don't rely on current based beta gain of a bipolar transistor, you can often drive them with CMOS logic circuits.

Make sure you use high speed flyback diodes because FETs are very vulnerable to the reverse polarity spikes from an inductive load. Make sure you use a small capacitor at the motor to clamp the really high spikes.

I wasn't going to drive an h-bridge with an h-bridge. I just wanted to know if I could simply amplify the out put from a low current h-bridge to get the current needed to drive the motors.

I want to send the PWM pulse train through some kind of amplifier and the forward reverse line through a voltage ramp, probably the same type of amplifier, and attach that to my motor.

I'm trying to lower the parts count on the motor driver to make it smaller.

I was told I could probably do this with a couple of op-amps.

Eljin

Isn't that driving an H-Bright with an H-Bridge?

If you use FETs and CMOS logic, you need 2 AND gates, 2 inverters, the 2 p-channel and 2 n-channel transistors, a small cap for the motor, and 4 high speed/current switching diodes.

Opamps are great, but tend to be pretty slow. You probably won't be creating a high efficiency amplifier, so your frequencies will be in the low audio range, but still, something a long the lines of a fast opamp (TL092) or something.