5725A
Instruction Manual
(ICAL, TP208) with the same amplitude and polarity as the current amplifier input voltage. The calibration amplifier output is measured by circuitry within the 5700A during calibration of the 5725A current amplifier. The calibration amplifier output is fed back to the 5700A Oscillator during ac current operation.
The feedback signal from the precision shunt is applied to both the inner and outer loop error amplifiers (ISENSE HI, ISENSE LO , pages 1 and 2). The error amplifier section drives the output stage (TP204) so that the voltage across R272 is
Output Stage Section |
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Refer to page 1 of the Current Amplifier schematic. Components U203, R203, R204, and R209 convert the bipolar
In response to a positive polarity error amplifier output (TP204), the current through R209 increases. This same current flows into pin 2 of U203, causing the voltage drop across R203 to increase. The voltage across R203 is applied to the positive input of U204A. U204A drives Q203, Q205, and Q207 until the voltage at the emitter of Q207 is identical to the voltage at the
The quiescent operating point of the output devices is fixed by the bias current of U203 and current source CR205 at about 1A. There is no output stage bias adjustment.
Capacitor C235 and resistors R256 through R260 provide a tertiary feedback path that guarantees stability when the 5725A is driving the specified inductive loads.
Monitor Section |
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Refer to page 1 of the Current Amplifier schematic. Components U211C and D, U210C, RT203, CR207, and associated resistors and capacitors make up the temperature- monitoring circuit. Heat sink temperatures above approximately 85°C signal the ITEMPM fault condition.
Components U207, R280 through 284, and C234 generate a negative voltage at TP207 (DRIVE MONITOR) that remains less than 3.1V in magnitude when the output compliance voltage is within the linear operating range of the output stage. The output compliance voltage is not measured by the drive monitor circuit; an overcompliance condition is inferred from excessive error amplifier output.