5402 Low Noise Current Amplifier

The Model 5402 is a low noise current input preamplifier designed for use whenever the signal source is a current source - for example, an electron multiplier, ion collector, photo multiplier, or photodiode, or when measuring sample impedances. The gain (transimpedance) is switch selectable with six settings enabling the amplifier, on its most sensitive range, to detect fractions of a picoamp without noise degradation.

The unit has a bandwidth of 100 kHz on its highest gain (1 GV/A) and greater than 4 MHz on its lowest gain (10 kV/A), while still maintaining low input current noise ranging from 25 fA /√Hz on the 1 GV/A range to 5 pA/√Hz on the 10 kV/A range. The gain setting is changed by simply pressing a push-button, with the present setting being indicated by an LED. The setting is retained when the power switch is turned off and restored when it is turned on again.

Switch selectable output filters allow AC or DC output coupling, and three choices of low pass filtering which can reduce overall noise, especially when working at high gains if the full bandwidth is not required.

The Model 5402 is powered by two internal lithium-ion rechargeable batteries which allow operation for up to 48 hours on a single charge. This method of powering delivers the lowest possible noise as well as allowing isolated operation, preventing problems which might be caused by ground loops.

A plug-in line power supply, model PS0112, is included which is capable of recharging the batteries in one model 5402; recharge time is a maximum of three hours.
  • Documentations +

  • Specifications +

     Mode  Single-ended
     Coupling  DC
     Connector  BNC socket
     Maximum safe input voltage  ±20 V DC
     Input Bias Current  1 pA typical
     Input Referred Voltage Noise  2.5nV/√Hz typical
     Input Referred Current Noise  See Table Below
    Gain & Frequency Response
     Gain  Switch selectable (6 settings) to 1G, 100 M, 10 M, 1 M, 100 K, 10 K V/A
     Accuracy  ± 0.5 dB
     Flatness in pass-band  ± 0.5 dB
     Frequency Response  See Table Below
     Cut off frequency settings:
         10 M  Full bandwidth
         1 M  1 MHz ± 150 kHz
         110 k  100 kHz ± 15 kHz
    Output Filters
     Output Coupling (high-pass)  When set to DC, amplifier is DC coupled.
     When set to AC, low- frequency cut off is 0.1 Hz
     Output Filter (low-pass)  Low pass Butterworth filter with 18 dB/octave roll-off filter reduces overall noise, especially when working at high gains, if full bandwidth
    is not required.
     Impedance  50 Ω
     Connector  BNC jack
     Max voltage swing  > 5 V pk-pk
     Polarity  Current flowing into the input produces a positive output voltage
     Protection  Output is short-circuit protected
     Internal  Rechargeable lithium ion batteries provide up to 48 hours of use.
     Batteries recharge automatically when DC power is connected. Recharge time is max of 3 hours
     External  9 V DC @ 350 mA max
     Connector  1.3 mm DC power socket, inner pin positive, outer barrel negative
     Excluding connectors   3½" w x 1¼" d x 2¾" high
     (85 mm x 31 mm x 71 mm)
     Including connectors   4½" w x 1¼" d x 2¾" high
     (114 mm x 31 mm x 71 mm)
     Weight  7.5 oz. (210 g) excluding optional power supply
    Typical Frequency Response Table
    Gain   Bandwidth (–3dB) with
    Cin = 10 pF 
     Bandwidth (–3dB) with
    Cin = 1 nF 
     Input Referred
    Current Noise (typical
     10 K  > 4 MHz  > 600 kHz  5 pA/√Hz
     100 K  > 2 MHz > 400 kHz   880 fA/√Hz
     1 M  > 1 MHz  > 200 kHz  300 fA/√Hz
     10 M  > 800 kHz  > 100 kHz  140 fA/√Hz
     100 M  > 250 kHz  > 50 kHz  65 fA/√Hz
     1 G  > 100 kHz  > 25 kHz  25 fA/√Hz