# Function generator amplification

1. Sep 4, 2007

### DkC

Hello,
How can I increase voltage and current from a function generator and still keep an accurate waveform? I want to provide AC power to an electromagnet but my function generator does not have the power to drive it.

Any help will be greatly appreciated.
Thanks

2. Sep 4, 2007

### Staff: Mentor

You could use an audio amplifier, like you would use to drive a speaker with music. Just be sure that the electromagnet has an input impedance that is compatible with the power amplifier's output impedance and output power handling capability.

3. May 16, 2011

### bkabi

can the audio amplifier be used for a pulse with 10Mhz frequency?

4. May 16, 2011

### vk6kro

No.

Whatever amplifier you use must have a bandwidth at least equal to the bandwidth of the signal.

For example, a 10 MHz square wave would only emerge from the amplifier as anything like a square wave if the amplifier had a bandwidth of 100 MHz or better.

This is because a square wave consists of the fundamental frequency (10 MHz in this case) plus a large number of odd harmonics.

So, the 10 MHz squarewave consists of sinewaves at 10 MHz, 30 MHz, 50 MHz, 70 MHz, 90 MHz etc and all of these have to be amplified and kept in the same proportion to each other as they start with.

5. May 16, 2011

### bkabi

So in that case what do you suggest if I want to increase the voltage/current output of my function generator which produces 10MHz pulses??

6. May 16, 2011

### vk6kro

That depends.

How much signal does the function generator give now, and how big do you want the pulses to be?

Also, do you want to just amplify the 10 MHz square waves, or do you want to amplify anything that comes out of the function generator at all frequencies?

7. May 16, 2011

### bkabi

The signal is upto 10Vp-p. For my use , I use it as a pulse generator with peak voltage 5 and low voltage 0. The pulse duration is 1microsec(100ns pulse on time 900ns pulse off time). My problem with this is that the "current" output is low which I want to amplify. The voltage output is fine but will be great if this can also be doubled.

Thanks

8. May 16, 2011

### Carl Pugh

Electromagnets are EXTREMELY inductive.
What is the inductance of your electromagnet.

9. May 16, 2011

### vk6kro

The early part of this thread is from 2007, so the inductor question is now obsolete.

Regarding the function generator, if you wanted to just amplify the square-topped waveforms to give greater current, there are some line driver ICs that would be fast enough to do this.

For example there is the 74F365 which has rise times of a few nanoseconds.

There are also some very fast opamps available. These would be able to reproduce a complex waveform, but they require very careful design to avoid instability.