VF-180 MICROELECTRODE AMPLIFIER

The VF-180 is a high input impedance voltage follower for intracellular voltage measurements. The VF-180 has a current injection capability and possesses a true current generator which adjusts the injected current so that it is always proportional to the command pulse amplitude (1 nA for 100 mV) and independent of the charge resistance.

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Standard head-stage is HS-180. Three other head-stages are available for the VF-180. Choice is dependent upon current injection requirements. Head-stages can be interchanged without internal recalibration of the instrument. Each head-stage is fitted with a miniature, coaxial electrode holder with driver shield. Only 5 mm in diameter, gold plated and 50 mm long, the electrode holder is a masterpiece in design.

• High impedance head-stage
• True current generator
• Negative capacity compensation
• Oscillation burst (tickle) facility
• Electrode resistance compensation (Bridge)

Rise time (HS-180)

• 0.5 us with pulse applied directly to the input
• 20 us on 10 MOhm load fully compensated for input capacitance

Input capacity

• Around 1 pF, adjusted to zero by negative capacity compensation

Frequency response

• 2 MHz on x 1 setting - 3 dB at 500 kHz on x 10 setting
• Low pass filter : - 3 dB at 1 or 10 kHz

Noise spectra

• Noise measured after amplification (x 10 gain setting with HS-180 probe)
• Zero source resistance : 10 µV RMS with 1 kHz filter
• 10 MOhm source resistance : 30 µV RMS with 1 kHz filter

Notch-filter

• 50 or 60 Hz Notch-filter

Negative capacity compensation

• 0 to 33 pF

Voltage measurements

• Gain : x 1, x 10. Junction null : +/- 200 mV

Electrode resistance compensation (Bridge)

• Two scales on a ten-turn dial. 100 MOhm/1000 MOhm with HS-180

Current injection

• Input for current command (1000 mV = 1 nA with HS-180)
• Maximum leakage current : 300 fA adjustable to zero
• Calibrated 1 nA injection for resistance measurements

Power supply

• 220 V/50 Hz, 110 V/60Hz

Head-stages

The VF-180 is delivered complete with one HS-180 head-stage (ref. 013-08) and with one SM-150 electrode-holder (for electrodes of diameter 1.5mm). Please specify on order if you want to receive other types of head-stage or electrode-holder.

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