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ultra low power small signall amplifier

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david_0607

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Hi All,

I need ultra low power small signal amplifier (bjt, fet, or mosfet, single stage, gain arround 10),
the amplifier is battery operated 1.5-3.3volt,
stanby current sould be less than 5uA,smaller is better

i don't know how to start, have try some calculation, but seems can not tolerate wide supply variation, let say if calculation made on 3 volt supply, the circuit will not work for 2 volt supply,

pls some body help me, or share any idea

best regard

davids
 

keith1200rs

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What bandwidth? There are opamps around with a quiescent current of less than 1uA.

Keith
 

david_0607

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Hi Keith,

the amplifier intended to amplify a 100Khz signal, bandwidth is not critical, gain at least 10,
Yes I know there are some op amp that suitable for this, the problem is, I want it will be very low cost, that is why I willing to design 1 transistor circuit, but I really don't know how to design such ultra low circuit from an ordinary transistor, or the question is : is it possible to do that with a single ordinary transistor?

best regard

davids
 

keith1200rs

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What sort of signal swing do you need? Is it a small AC signal or DC? Normally you might look at a JFET for a low current amplifier but your supply voltage is too low. I think the micropower opamps will not have enough bandwidth at 5uA. A discrete bipolar could probably manage it. For RF design there are some devices which are optimised for low current, so still give a good bandwidth at very low collector currents (eg >1GHz at 10uA). I am not sure if there are similar devices for low frequencies, but it is possible. If you want to simulate something, the 2SC5507 looks OK but it is an RF transistor so good layout will be critical if you decide to use it. It has another part number from NEC, but I cannot remember off hand what it is.

Another option may be an HEMT. Again, they are RF devices so you will need careful layout use them. Agilent make quite a few which are readily available. I am not sure how well the perform at low currents but they have pretty low threshold voltages so are usable at low voltages I think.

Keith.
 

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