Axon Axopatch 200B, Theory Of Operation

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108 • SPECIFICATIONS
Axopatch 200B, Copyright 1997-1999, Axon Instruments, Inc.
monitoring of cell membrane potential, but the speed setting is still determined by the
actual electrode resistance and not only the remaining uncompensated resistance.
The speed of the current clamp depends on the MODE setting (NORMAL or FAST), the
time constant of the cell and the pipette resistance.
10 - 90% rise time 10 - 90% rise time
(overshoot) (overshoot)
Rp Rm Cm I-CLAMP NORMAL I-CLAMP FAST
1 M
Ω
0 M
Ω
0 pF 15 µs (10%) N/A
1 M
Ω
500 M
Ω
33 pF 350 µs (0%) N/A
10 M
Ω
0 M
Ω
0 pF 200 µs (20%) 20 µs (<1%)
10 M
Ω
500 M
Ω
33 pF 250 µs (10%) 10 µs (<1%)
50 M
Ω
500 M
Ω
33 pF 500 µs (30%) 150 µs (<1%)
HL-U Pipette Holder
HL-U holder mates to threaded Teflon input connector of the CV headstage. Post for
suction tubing is 1 mm OD. HL-U holder accepts glass 1.0-1.7 mm OD. Supplied with
silver wire. Optional HLR-U right-angle adapter and HLB-U BNC adapter are available.
Capacitance Compensation
Pipette Capacitance
Fast
τ
: 0.2- 2 µs
Fast Magnitude: 0 - 10 pF
Slow
τ
: 0.1 - 10 ms
Slow Magnitude: 0 - 1 pF
These controls are used to charge pipette capacitance. In I-CLAMP modes they act as a
negative capacitance.