Owner’s Guide
47
Technical Aspects
The Neuro Amp EX and other ADInstruments front-ends have been designed to integrate
fully into the PowerLab system. The Neuro Amp EX is essentially an extension of the
PowerLab’s input amplifiers. The amplification and ranges off ered in LabChart result
from the combination of both pieces of hardware.
The PowerLab provides control and low-voltage power to front-ends through a special
expansion connector called the I
2
C bus. Front-ends are also connected to the analog
inputs of the PowerLab via a BNC cable, through which they send the amplified and
filtered signals. The overall operation of the Neuro Amp EX can be better understood by
referring to Figure 9–13 on page 51.
The headstage is a diff erential in/diff erential out amplifier with a fixed gain of ×100 and
a 10 Hz high-pass filter. The amplifier drives a diff erential signal into the Neuro Amp EX.
Power is supplied through the connector. A reference pin is a current-limited isolated
ground return to protect against excessive auxiliary current. The overall operation of
the Neuro Amp EX headstage can be better understood by referring to Figure 9–12.
+7.5 V
+
-
-7.5 V
+ Signal
- Signal
10 Hz
HPF
Input
Protection
Ref
An audio signal output, capable of driving headphones or powered speakers, is provided
by tapping off and buff ering the output stage.
The control for the various filters and gain stages in the Neuro Amp EX is provided by on-
board microprocessors, which also communicate with the PowerLab over the I
2
C bus.
Figure 4–9
Block diagram
of the headstage
amplifier
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