High Voltage OP AMP needed

Or perhaps simpler, a high voltage ramp generator. The SuperTex AD-D12 goes up to 500V, but the example oscilloscope trace in the app note demonstrates a a +/- 50V (100v nom) 1 kHz circuit very close to your requirements.

An opamp can not create a sawtooth and it would need a much larger bandwidth than the repetition frequency. Make a current source charge a capacitor, (optionally buffer it with a complimentary emitter follower for higher current capability), and trigger a thyristor to the negative rail when the desired voltage is reached. cheap and simple.

On Fri, 23 Mar 2007 14:49:39 +0100, Casper Budtz-J?rgensen Gave us:

Dude, the op amp is a driver. Use a transistor or FET after it for the real work.

I'll second the Apex recommendation. I've used their PA84 to deliver a +/-100V signal biased at 200 V (eg +100 to +300 swing) at well over 20 kHz. It was humbling to use one of their slick little TO-3 amps to replace my entire prior HV amp design, which had series- stacked transistors and fancy bias to be able to handle the voltage range that the Apex handled without fuss.

Best regards.

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Yup. I've used Apex products, and it *is* humbling. Also, a little pricey and typically long lead times. The PA84 shows almost $150USD and lead time of 5 or 6 weeks.

There are a couple of options available to the OP if Apex product is looking a little uncomfortable. First off, he can bootstrap a regular voltage op amp to handle the higher volotages (a trick developed by the National Semi gurus in the early days of IC op amps, AFAIK). Here's a good link which goes into a little detail on how to do this on the cheap:

Another, much easier way to skin the cat might be to just do an application-specific circuit. Since the OP basically wants a 60V sawtooth, he could use a transistor constant current source to charge up a cap, and then use a 555 to drive an NPN transistor with short

Cheers Chris

On Sat, 24 Mar 2007 11:07:45 -0500, John Fields Gave us:

A piezo stack amplifier we designed had two 2kVA transformers and did

It was used on a lathe in a very controlled micro-machining tool head that had micron level accuracy. It was used to cut plastic contact lenses with optical quality surface Q.. One application was 1 inch diameter lenses used one race horses.

The tool could cut a square shaft out of a spinning rod on a lathe.

One could squeeze the stack and it would exhibit voltage as well (of course).

Our client was:

In message , Casper Budtz-Jørgensen writes

Well back in the '80s I used a signal generator and a HH amplifier( like the ones Slade used back then, the ones with the green electro-luminescent panel)

Is Figure 6 another "EDN IQ test" ? (dodgy EDN schematic)

Figure 6:

it looks to me that RB and RF should connect to Vout where they cross. or am I misunderstanding the purpose of RB?

Bye. Jasen

Well thanks to everyone - dude included - for their replies. I certainly got the info I need. I will check out the Apex amps. In case you are interested, I am making a Langmuir probe system for plasma diagnostics. I have a working system using an Exar2206 wave generator to drive a handful (its a multiple probe system) of OPA452 Op Amps that deliver the

Thanks again,

Casper

Casper Budtz-Jørgensen wrote:

(snip)

I agree. They lost a dot.