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nandopg
Joined: 26 Apr 2001
Posts: 239
Helped: 3
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 11 Jul 2002 3:01 Low noise inverter chip for biasing GaAs Fet's gate |
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I am looking for a low noise inverter chip (8pins) to generate the negative voltage for biasing GaAs Fet's gate.
I tried the Maxim and Linear Technology chips. They performed good but they did'nt accomplish with the temperature range requiride.
Does somebody suggest me some other manufacturer?
Thanks in advance
NandoPG
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Bagster
Joined: 08 Nov 2001
Posts: 47
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| 15 Jul 2002 15:00 gaas fet bias |
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i know quite a few.
for single stage, you can either do this using a custom IC or using discrete components. i am assuming you want to bias at a fixed voltage and with a constant current. what is the gate current, how much do you need. What FET are you using.
If it is low then you can use a crude method. A lm555cm timer configured as a free running oscillator, two diodes an a capacitor or two added to this can generate a unregulated negative voltage. Use a simple BJT set up a circuit that will bias the DUT at a known voltage and current. (if you need a schematic let me know).
Solution 2.
Zetex make asics that do all this for you. There are loads of flavours for every situation.
solution3
NJRC do a device based on the icm7660 switched capacitor invertor. This has two integrated opamps to help set up the bias conditions.
If you need anymore info ask
Regards
Bagster 
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shanren
Joined: 12 Oct 2001
Posts: 106
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| 17 Jul 2002 11:36 |
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hi,what temp range you request?and how much current do you need?i have used a -40 to 85 degree ,it is a pump converter 7660.many company have such chips,such as maxim,linear tech,national.if the noise is too high,use a rc or lc filter.or use a LDO to get better performance.you can visit:
h**p://www.maxim-ic.com
h**p://www.linear.com
h**p://www.national.com
h**p://www.ti.com
they have many pumps ,even sot23.they also have many LDOs.
hope this can help you.
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