Waveshaper !!

You fail to state if the TTL signal is a square wave that you want to merely go from some unspecified negative voltage to some unspecified voltage. Perhaps you might have TTL pulses that should alternately change the output polarity? 200nSec is rather slow, and opamps are not needed. What kind of homework quiz is this anyway?

A capacitor and a couple of diodes and resistors could do it. Look up "clamp circuit".

If you're only asking for answers to a homework question, then go away.

Good Luck! Rich

This sounds like a classic application of a comparator, but a fast opamp may serve and provide the larger than normal output swing. One with a CMOS output will provide an output swing to almost its supply rails. An examples is CA3130.

Bias one input of the opamp with about a constant +1 volt (the gray area between a TTL low and high) and connect the TTL signal to the other input. If you want the output high to correspond to the input high connect the TTL input to the

• input. If an inversion is needed, to the - input.

On Thu, 19 Oct 2006 20:38:50 -0700, Matrix top-posted:

It sounds like homework, but apparently you're really trying. Have you tried a comparator?

Good Luck! Rich

Well you'll need a relatively fast op-amp, and you did not mention what the output voltages should be.

Just set the negative input of the op-amp to the middle of the TTL swing, with a couple of resistors. Feed the TTL input into the positive op amp input. The output should be swinging from rail to rail, or however far that op-amp will swing.

For extra credit, put a 1K resistor in series with the positive input, and put a 100K resistor from output to positive input. This will provide a little positive feedback and make it snap over a lot faster, especially at low frequencies.

A better choice would be a comparator-- they're designed for just this application.

Note- for 5MHz operation you'll need to use good bypassing and a ground plane and short leads--- it's not likely to work at all well on a plugboard.