26
Publication 5720-001 REV1.0
Setup
Other Gain Range Selection Considerations
The intrinsic noise of the current measuring circuit is a function of the bath clamp
feedback resistor with a larger resistor offering lower noise and greater signal resolution.
For comparisons, the following measurements were made with a shorted input, with the
standard 0.5 µF capacitance model cell, and with a 0.22 µF capacitance modified model
cell. All readings were recorded at 1 kHz (8-pole Bessel) and are RMS.
A lower value feedback resistor increases the speed of the bath clamp and can handle
larger currents without saturating, important when recording from high expression
oocytes.
Feedback
Resistor
Noise
Shorted Input
Standard Model
Cell (0.5 µF)
Modified Model
Cell (0.22 µF)
10 kΩ
75 pA
6.0 nA
4.4 nA
100 kΩ
28 pA
5.5 nA
4.4 nA
1 MΩ
22 pA
5.0 nA
4.0 nA
Gain
Select
Headstage
Resistor
I
m
output
range (V/µA)
I
m
max output
(µA)
Maximum
meter reading
x0.1
10 kΩ
0.01 - 1.0
10 - 1000
199.9 µA
x1.0
100 kΩ
0.1 - 10
1 - 100
19.99 µA
x10
1 MΩ
1.0 - 100
0.1 - 10
1.999 µA
