Neuralynx Headstage-27 Amplifier User’s Manual
The Neuralynx Headstage 27 (HS-27) Amplifier is the active electronic part of the Electrode Interface Board / Headstage / Tether system. It provides 27 channels of Unity Gain amplification (buffering). It also provides connections for the electrode inputs to the EIB-27 and an output connector for a single cable 36-conductor tether.
The Headstage Amplifier size is approximately 35 mm high by 25 mm wide. One 37 pin micro-D connector is used for tether connections. One connector on the bottom of the board is used to connect the Headstage Amplifier to the Neuralynx Electrode Interface Board.
Low noise, low power, low input bias current Opamps have been used on this device instead of the traditional “Source Follower FET circuit” used in the traditional headstage amplifier design in order to: obtain exact unity gain which greatly improves Common Mode Rejection Ratio (CMRR) performance for the entire recording system for artifact and other common mode noise signal rejection; lower output impedance to reduce noise susceptibility of the tether and other signal cabling; provide integral antistatic protection on each input channel; insure low input bias current levels; and eliminate signal distortion.
NOTE: Because an Opamp is used for the unity gain buffer amplifiers, special care and attention must be given to the power supply design and power application and removal sequencing. The input protection circuitry will lower the input impedance if the input voltage exceeds powersupply voltage. This can occur by either raising the input voltage signal above the power supply voltage or by the loss of power supply voltage. The Headstage-27 contains active power supply voltage monitoring circuitry, which will NOT apply opamp power supply voltages until the power supply voltages exceed the minimum normal operating voltage. The Neuralynx EEG/Reference Panel contains power supplies, which properly sequence power supply voltage and monitor headstage currents.
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