Single Unit Activity Filter/Amplifier (SUA)

The TREC Single Unit Activity Filter/Amplifier (SUA) is a multichannel, differential input main filter/amplifier for neurophysiological applications (e.g. extracellular recording with multiple microelectrodes). This SUA-Filter/Amplifier combines a band pass filter with variable cut-off frequencies and variable signal amplification on each channel in one instrument.

Key features:

  • 8 amplifier channels
  • Low-noise amplifier technique
  • Differential input amplifier
  • Individual gain settings from x50 up to x5000 (in different steps)
  • Bandwidth 500kHz ... 20kHz (in different high pass filter steps)
  • AC coupled input circuit
  • Low noise technique
  • Integrated power supply
Dimensions and Weight: Depth (mm): 330mm
Width (mm): 450mm
Height (mm): 270mm
Weight (kg): 15kg
Power Supply: Supply voltage (V): 115VAC or 230V AC
Power Consumption (W): 50VA
Environmental conditions: Operating temperature range: +10°C to +40°C
Transport temperature range: +10°C to +40°C
Humidity: 20% - 80% RH (non-condensing)
Input data: Max. Filter input voltage: ±6V
Single Unit Activity (SUA) Bandpass Filter/Amplifier: Gain: 50, 100, 250, 500, 1000, 2500, 5000
Input impedance: 1M?//30pF
Low Pass cut-off [kHz]: 2 / 5 / 10 / 20 kHz
High Pass cut off [Hz]: 0.5 /1 / 2 kHz
Filter Characteristik: Butterworth
Input connector: BNC
Output Connector: BNC
Max. Output voltage swing: ±10V

Features

Figure 1: 8 channel Single Unit Activity Filter/Amplifier (SUA-08)

The SUA-Filter/Amplifier contains a high-gain, low-noise differential amplifier stage followed by low frequency and high-frequency filters. The amplifier has a differential single unit activity (SUA) bandpass filter–amplifier. The amplifier offers two levels of signal gain (x10, x100) in a first stage and 4 additional levels (x5, x10, x25 and x50) in a final amplifier stage (see Figure 2).

The amplifier has a band pass characteristic for single unit activity (SUA) 500Hz…20kHz. The cut-off frequencies are independently selectable for low pass filter 2, 5, 10, and 20 kHz and for high pass filter 0.5, 1 and 2 kHz.

The SUA-Filter/Amplifier is modular system that is available with different numbers of channels (1-8) and with integrated Audio Monitor (see figure 3).

Figure 2: Block diagram of one SUA-filter/amplifier section

Furthermore each SUA-Filter channel is equipped with a two level window discriminator. The window discriminator is an instrument for the separation of single neural spike trains from a multiunit recording containing more than one neural element. The window discriminator of the SUA-Filter produces a window in amplitude. The window can be adjusted in height, above or below baseline. The trigger point is set by a continuously adjustable level control for either positive or negative slope detection. The signal and both window levels are multiplexed so that only one channel of the oscilloscope is necessary. A reliable description of the activity pattern of a single, well-isolated neuron is the key to many important experiments in neurophysiology. Once the quality of the recorded signal has been optimized and enhanced by the proper microelectrodes, amplification, and band pass filtering of the SUA-filter/amplifier module, the yield is determined by the power and flexibility of the spike discrimination and processing system. The TREC modular signal conditioners have been optimized for this purpose.

Figure 3: SUA-Filter/Amplifier (7 channel) with integrated Audio Monitor module and loudspeaker