Differential Pre-Amplifier, 4 channel


The Differential Pre-Amplifier, Model DPA-4 is a miniature 4-channel, high impedance, differential input preamplifier that is designed for low noise recordings from excitable tissue. It is intended for extracellular recording in conjunction with Thomas Tetrodes and Thomas single microelectrodes. It can be used in a number of research or teaching applications requiring extracellular neurophysiological recording from excitable tissue.

Key features:

  • 4 Channel, DC or AC coupled, differential input
  • High impedance input
  • Adapted to be used with Thomas Tetrodes
  • Other electrode adapters on request!
  • Battery power supply available to avoid noise pickup from power lines
  • Low noise
  • Small size, lightweight and low price
Dimensions and Weight: Length (mm): 40mm
Width (mm): 34mm
Height (mm): 7,5mm
Weight (gramms): 26g
Power Supply: Supply voltage (V): ±6V DC
Supply current (mA): ±5,3mA
Amplifier Data: Gain per channel: 9,9
Number of channels: 4
Bandwidth per channel: 0...40kHz
Input circuit per channel: DC-coupled (AC on request)
Common mode rejection ratio/channel (CMRR)
Per channel at f=50-60Hz: 100dB
Input referred noise voltage per channel: 16 nV/Hz
Crosstalk attenuation between channels: 55 - 73dB
Environmental condition: Operating temperature range: +10°C to +40°C
Transport temperature range: +10°C to +40°C
Humidity: 20% - 80% RH (non-condensing)


The DPA-4 is connected to metal microelectrodes or tetrodes for providing an initial tenfold amplification stage. Ideally Thomas RECORDING quartz glass insulated platinum/tungsten microelectrodes or tetrodes are used to yield optimal recording results with high signal amplitudes and low noise levels.

Figure 2: DPA-4 size comparison to a standard AA-size battery

Figure 3: Connection of a Thomas Tetrode to the DPA-4 input socket

Figure 4.1 and 4.2: DPA-4 mounted to a manual xyz-manipulator together with a Thomas Tetrode

The DPA-4 is delivered as a DC-coupled preamplifier to yield optimal common mode rejection ratio (CMRR). An AC-coupled version is available on request. The DPA-4 is equipped with an additional common ground and reference electrode input. 

The aluminum case of the DPA-4 provides electrical shielding. Electrode damage is prevented by the very low bias current. The high input impedance ensures stable long-term recordings.

The DPA-4 has a small size and weight and therefore it is easy to integrate this amplifier in many recording setups. Special adapted holders for manual microdrives are available from Thomas RECORDING (see figure 4). Custom-made adaptations are possible


Beside the possibility to use Thomas microelectrodes and tetrodes, adapters for other microelectrodes for acute and chronic recordings are available.

To avoid additional noise pickup from the power supply there is a special designed accumulator power supply and a battery charger available for power supply of the DPA-4 (see figure 5 and 6).

Figure 5: Accumulator power supply for the DPA-4

Figure 6: Accumulator charger