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Magtrol Model 5210-2 Power Supply
User’s Manual
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eScription
Functionally, the circuit is a closed loop, current feedback amplifier regulating the output current at
the value set by the front panel controls.
DC current from the internal 35 volt power supply passes through the dynamometer coil connected
at the BRAKE connector J6, through the insulated gate field effect transistor Q1 (HEXFET), and
through a current sense resistor R13, R14 or R15 (selected by the RANGE control). The voltage
drop across the current sense resistor is amplified by Operational Amplifier U1b and applied to the
non-inverting differential input of Operational Amplifier U1a. Amplifier U1a amplifies the difference
between the conditioned current signal from the sense resistor and the voltage from the front panel
current ADJUST potentiometer, R6. This amplified error voltage is applied to the gate of transistor
Q1 to control its channel resistance and thereby regulates the output current at the value set by the
ADJUST control.