HP (Hewlett-Packard) HP 85660B ユーザーズマニュアル

Al8 Negative Regulator provides -5.2 V, -10 V, and -40 V regulated voltages to the

instrument. All three supplies derive their reference from the 

 V supply on the Al7

Positive Regulator. The relationship of Al8 to A8 Rectifier, Al7 Positive Regulator, and A23
Motherboard is shown on the A8 schematic.

The -10 V supply is referenced to the 

 V supply by a resistor divider consisting of R5,

R6, and R7 connected between the two supplies. The voltage at the junction of R5 and R6 is
nominally 0 V. Any error is amplified by U2 to drive the series-pass transistor 

 The

entire unregulated portion of the supply, including the rectifier diodes and filter capacitor, is
floating; thus the collector of 

 is typically i-15 V. Current-sensing resistors Rl and R23

are connected between the emitter of 

 and ground. These resistors, along with R2, R3,

 and 

 form a current 

 protection network.

Overvoltage protection is provided by the -10 V crowbar   consisting of VR2 and CR26.
Further protection is provided by fuse F3. LED DS2 indicates the presence of an output

voltage.

The -5.2 V supply is also referenced to the 

 V supply by a resistor divider consisting of

R37, R38, and R39 connected between the two supplies. This supply is a double-regulated
supply, as its input is in the regulated output from the -10 V supply. Error amplifier 
drives the pass transistor Q2 via Q3. R32 and R33 are dropping resistors, so the power
dissipation in 

 is not excessive. R34, R12, R32, and Q4 provide current 

 protection.

Further protection is provided by 

 Overvoltage protection is provided by the -5.2 V

crowbar   consisting of VR4 and CR27. LED DS3 indicates the presence of an output
voltage.

The -40 V supply is referenced to the 

 supply by the voltage divider consisting of R24,

R25, and R26, designed so that the input to the error amplifier U3 is at 0 V. The output
of the error amplifier drives the Darlington connection of 

 and the series-pass transistor

 The input to the supply is floating, so the collector of 

 is typically at 

 V.

 current protection is provided by R17, R18, 

 and Q6. Further current protection

is provided by the -40 V crowbar   consisting of VR3 and CR25. The presence of an output
voltage is indicated by LED 

A18 1