High Voltage Amplifier

Audio analysers, such as the Audio Precision series have signal generators that for certain test purposes do not have a sufficiently high output voltage. That is why we have designed this ‘booster’ amplifier stage. It provides the same amount of voltage as a 300-W amplifier into 8 W. Applications for this amplifier include the testing of measuring filters or an automatic range-switching circuit.The amplifier can, with a ±75 V power supply, generate 50 VRMS, with an input signal of 5 VRMS from the signal generator. In other words, the voltage gain is set to 10 times. In many cases the full bandwidth of the generator is not available at maximum output voltage. For this reason the amplifier gain is a little more than what is actually required for this application.

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Materials

044036-PCB.pdf

Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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PCB

Download Gerber file: 044036-1.zip

Component list

Resistors:
R1,R16,R17 = 10kOhm
R2,R6 = 100Ohm
R3 = 1kOhm10
R4 = 10kOhm0
R5 = 5kOhm6
R7,R8 = 47kOhm
R9,R10 = 270Ohm
R11,R12 = 82Ohm
R13,R14 = 220Ohm
R15 = 1kOhm
R18,R19 = 27Ohm
R20 = 47Ohm
R21-R24 = 12kOhm
Capacitors:
C1 = 22pF
C2,C3 = 47µ F 25V radial
C4-C7 = 100nF (C6/C7: 100V!)
C8,C9 = 470µ F 100V radial
Semiconductors:
D1,D2,D5-D8 = 1N4148
D3,D4 = rectangular LED, red
D9,D10 = zener diode 22V 1.3W
T1 = BF470
T2 = BF469
T3 = 2SC2911
T4 = 2SA1209
T5 = MJE350
T6 = MJE340
IC1 = NE5534
Miscellaneous:
K1,K2 = cinch socket, PCB mount, T-709G from Monacor/Monarch
Heatsink, 2.5 K/W (e.g. Fischer type SK100, 50mm height)
PCB, order code 044036-1 from The PCBShop