Electronics > Projects, Designs, and Technical Stuff

New high voltage opamp - ADHV4702-1

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dzseki:
The problem with the CRT type amplifiers is that the good transistors for those are long gone...
For high bandwidth sanyo had a few hybrids VPAxx line where xx corresponds to speed 13 is 130MHz. These could do 40-50Vpp (single sided) at the specified bandwidth. Alternatively you could build discretely the cascode circuit, great high BW high voltage transistors wer MRF548-549, BFQ232-252, but again these are long gone...

Zero999:
If there's no DC to worry about and the bandwidth isn't massive, then one solution is to build a low voltage amplifier and connect a transformer to the output. Negative feedback can still be used to reduce the output impedance, but a lot of care needs to be taken to avoid oscillation, as the transformer will have some phase shift.

There's an example in the Art of Electronics.

Doctorandus_P:
The good old OP07 goes toe 44V (+/- 22V) and +/-30V diferential input voltage, and this is not too uncommon for opamps.

Power opamps such as for examle for audio amplifiers (LM3886) also go a lot higher.

But I suspect low power high voltage opamps are rare because there is not much use for it. Adding some transistors to the output and/or a voltage divider on the input takes care of most situations.

Stuff is also mostly going down in voltages and power. From the 200+V in those obsolete glass bulbs to less than 900mV core logic in FPGA's and fast processors.

A 30V 3A power supply used to be a lot more used 20 years ago than now (but still usefull of course) Having a few good quality adjustable 15V 1A supplies will be sufficient or even preferable nowaday's.

awallin:

--- Quote from: splin on February 15, 2019, 10:26:08 pm ---Quite impressive - +/-110V, Ibias 2pA max @25C, 8nV/rt(Hz), 170dB AVol, 160dB CMRR!
$21 each or $13.43 @ 1K (Mouser)
What are you going to use yours for?

--- End quote ---

I think we used Apex PA340 for driving slowly changing DC-voltages +/-100V to electrodes...
not sure from the specs if the AD part has lower noise or not..
https://www.apexanalog.com/resources/products/pa340u.pdf

splin:

--- Quote from: awallin on February 17, 2019, 06:01:23 pm ---
--- Quote from: splin on February 15, 2019, 10:26:08 pm ---Quite impressive - +/-110V, Ibias 2pA max @25C, 8nV/rt(Hz), 170dB AVol, 160dB CMRR!
$21 each or $13.43 @ 1K (Mouser)
What are you going to use yours for?

--- End quote ---

I think we used Apex PA340 for driving slowly changing DC-voltages +/-100V to electrodes...
not sure from the specs if the AD part has lower noise or not..
https://www.apexanalog.com/resources/products/pa340u.pdf

--- End quote ---

Much higher voltage, 350 v 220V but the noise is in a different league - 337uV rms in 10kHz BW v 0.8uV!

Vos max drift 250uV/K v 2uV

Ibias max @ 25C 200pA v 2pA

CMMR min 84dB v 140dB

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