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Voltage-Clamp Electronics

Quoc Thang NGUYEN qnguyen at darwin.bio.uci.edu
Tue Feb 22 21:02:59 EST 1994

Hi everybody, 

I am in the process of building a special-purpose voltage-clamp, because the 
commercial devices are either ill-suited to my purpose, or way too expensive.
Since no schematics are available, I need to design it (or reverse-engineer 
it...). The clamp has to have some kind of cell capacitance compensation. So 
far, I understand that the compensation circuit requires two controls: a 
variable time constant and a gain. The value of the time constant should be 
adjusted so as to match the one made by the cell's capacitance and the series 
resistance. The gain should be chosen so its value, multiplied by the 
injection capacitance, is equal to the capacitance to be compensated. 

Question: I had a look at commercial clamps and some of capacitance 
compensation circuits feature, in addition to the time constant and the gain, 
a phase control (Cm Phase, see for instance the Clampator I from Dagan Inst.). 
What is the role of this knob?

Any help from electrophysiologists would be greatly appreciated. Thank you in

Quoc Thang NGUYEN
Graduate Student
Laboratory of Cellular and Molecular Neurobiology
Dept. of Psychobiology
University of California, Irvine
Irvine, CA92717 USA
Phone: (714) 856 4730
Fax  : (714) 725 2447
e-mail: qnguyen at darwin.bio.uci.edu

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