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Duo 773 Electrometer intracellular Amplifier

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Duo 773 Electrometer

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Duo 773 Instruction Manual
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  • 2-channel intracellular amplifier
  • For intracellular dual or differential studies
  • Built-in active filtering
  • Comes complete with 2 probe headstages, normally one high impedance and one low impedance


  • Dual channel, single ended recording
  • Differential recording
  • Bridge circuit nulls electrode voltage drop
  • Assign low pass filter to either channel
  • Very high impedance channel can be used with intracellular ISE


  • Intracellular electrophysiology using sharp micropipettes
  • Brain slice intracellular recording
  • In vivo intracellular recording from brain and spinal cord

2-Channel intracellular amplifier for dual and differential studies

Headstage For Precise Positioning

For intracellular dual or differential studies, the Duo773 has separate negative capacity controls and built-in active filtering that allows the precise balancing of time constants for artifact-free differential measurement. Comes complete with two probe headstages, 10^15 Ohms & 10^11 Ohms probes to monitor signals from ion-specific micro-electrodes as well as KCl-filled electrodes. Two gold-plated, epoxy sealed miniature active probes can be positioned directly to the measurement site. Microelectrode holders containing an Ag/AgCl electrochemical half-cells plug directly into the probes. Stray capacitance can be reduced by placing the included driven guard shield over the microelectrode holder at the end of the probe.

Capacity Compensation

Channel A can compensate up to 10 pF of electrode shunt capacity and Channel B can compensate up to 50 pF.

Tickler Circuit For Penetration

A tickler circuit assists in cell penetration. The frequency and amplitude of the oscillations may be varied for differences in membrane thickness or cell size. The duration of tickle can be controlled either by using the momentary switch, a foot switch, or by applying a signal to the remote tickler input.

Active Filters

Low pass settings on a -40 dB/decade active filter vary the cutoff from 1 to 30 kHz. Either probe or bridge outputs may be selected for filtering.

Current Injection

Channel B can eject current through the microelectrode by applying a command signal to the stimulus input connector; the resulting output from the probe will then be a constant current replica of the input signal. Two ranges of current delivery are provided: 50 nA and 500 nA or by an external source. This source can be useful for delivering hyperpolarizing currents to stabilize the cell membrane potential and as a holding current for microiontophoresis.

Bridge Balance

Subtracts the excess electrode voltage associated with delivering current through the recording micropipette. Electrode resistances up to 1000 MΩ can be balanced in two ranges. The balanced signal is available from x10 or x50 front panel output connectors.

Independent Outputs

The Duo773 has an output for each probe independent of gain filtering or balancing. In addition the Duo773 has a 10x and a 50x output for easy integration to most data aquisition programs.

Typical Setup

Optional Holders For Intracellular Amplifiers

Duo773 Unpacking & Setting Up Your Intracellular Amplifier


HEADSTAGE (PROBE) 712P (red, port B) 715P (blue, port A)
GAIN x1, x10 x1
INPUT CAPACITY COMPENSATION  +10 to -50 pF 0 to -10 pF
  Input shorted 712P 
  20 MΩ carbon resistor
  10-90% direct input small signal
  10-90% through 20 MΩ (-C "on")

1 µs, typical
25 µs, typical 
  Internal DC Current
  Externally commanded Current 712P (red, port B)
  External current command factor
  Current monitor
  Bridge balance
  Bridge amplifier gain

± 50 nA low range, ± 500 nA high range
± 500 nA low range, ±5 µA high range
20 mV/nA low range, 2 mV/nA high range
100mV/nA low range, 10mV/nA high range
3V low range, 10V high range
0-100 MΩ, 0-1000 MΩ
x 10, x 50
LOW PASS FILTER 40 dB/decade, continuously variable 1-30 kHz
Fuse (Older models) 120 V: 0.5 A, fast, 0.25x1.25” USA
230 V: 0.25 A, fast, 0.25x1.25” USA
Fuse (2019 models) 120 V: 0.5 A, fast, 5 x 20 mm metric
230 V: 0.25 A, fast, 5 x 20 mm metric
  Accuracy and resolution

3.5-digit LED
200 mV, 2000 mV, 20 V, 200 nA, 2000 nA 
1 digit

17 x 5.25 x 10 in. (43 x 13 x 25 cm)
Diameter: 12 mm Length: 34mm 
POWER 95-135 V or 220-240 V, 50/60 Hz 
SHIPPING WEIGHT 15 lb. (7 kg) 

* Although injected currents are “constant,” the maximum current in a given situation will always be limited by the system compliance of 10 V.

**The 712P headstage may be used on either A or B channels, however Current Injection specifications do not apply when used on channel A. The 715P headstage may not be used on the B channel.


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Replacement probe for Duo 773 Electrometer - Port A.

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Driven guard shield for FD223AP probe

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Replacement probe for Duo 773 Electrometer - Port B.

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Footswitch for A310

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Rack Mount Kit, 5 1/4-in. high

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