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[moved] H-Bridge for low current loads (biomedical sensors

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Hello all,

I'm trying to figure out an H-bridge circuit that enables me to drive a low current load. With motors and other high current loads, the FETs have no problem turning on and off since the driving voltage is high enough. What about low current loads? how to alternate polarity for a load driven by a small signal? any ideasfor circuits that might work is appreciated.

Cheers,
Moataz
 

Hi,

Could small signal BJTs be used instead? How small is the signal mentioned? Not having thought much about it, maybe nanopower op amps (as comparators) would be able to source/sink the low current, depending on how "low current" actually is.
 

Hi,

Give specifications with values and units.

Real example:
I made a constant current supply. The "low current" version is able to supply up to 250A (the high current version is for 6000A)

Klaus
 

d123 said:
Hi,

Could small signal BJTs be used instead? How small is the signal mentioned? Not having thought much about it, maybe nanopower op amps (as comparators) would be able to source/sink the low current, depending on how "low current" actually is.
Click to expand...

The signal varies in the range of 50mv to 1V, to be supplied to a filter of around 1K ohm total impedance (or less).

- - - Updated - - -

I will rephrase my question:

Application: excite a 2-port network with reversible-polarity small signal.

Signal: 50mv~1V p2p @ 1MHz

Would an H-bridge work (I guess not)? and at what MOSFET sizes?
 

With the few information given up to now, it sounds like you are rather looking for a linear differential output amplifier than a switching "H-bridge".
 

Depending upon your voltage range (if you can tolerate only positive voltages, for example) you might be able to use a basic dual mux switch, such as Maxim MAX4639?
 

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