High-voltage amplifier uses simplified circuit
Edited by Bill Travis
Jui-I Tsai, Jun-Ming Shieh, Tai-Shan Liao, and Ching-Cheng Teng, National Chiao Tung University, Taiwan -- EDN, October 14, 2004
Many scientific instruments and sensors need ac high-voltage drive. High-voltage drive is useful for driving electrodes in many applications. The challenge is to boost the output of a conventional op amp to high voltages. Available ac high-voltage amplifier modules are limited to approximately 1200V p-p. This Design Idea presents a simplified ac high-voltage amplifier that uses complementary, cascaded NMOS and PMOS transistors (Figure 1). The OP07 op amp has low input-offset voltage, low input-bias current, and high open-loop gain. These attributes make this op amp useful for high-gain instrumentation applications. In addition, the OP07 features excellent stability of offsets and gain over time and temperature. The ac gain of the LM356 stage, which R3, R4, R7, and R9determine, is approximately 100.
The high-voltage MTP2P50E p-channel MOSFET has maximum drain-to-source- and gate-to-drain-voltage ratings of 500V. The high-voltage BUK456800B n-channel MOSFET has maximum drain-to-source- and gate-to-drain-voltage ratings of 800V. Q1 through Q6 are PMOS transistors, and Q7 through Q12 are NMOS devices. These FETs are well-suited for high-voltage cascade circuits. They connect symmetrically in series to increase their overall breakdown voltage for power applications. The bias-voltage circuits comprise separate biasing-resistor pairs R10 to R13 and R14 to R17; the result is a symmetrical output of the high-voltage amplifier. Figure 2 shows a sinusoidal input of 8V p-p at 100 Hz and an output of 1800V p-p. Figure 3 shows a sinusoidal input of 750 mV p-p at 2 kHz and an output of 200V p-p. The total power bandwidth of the circuit is approximately 200 kHz.
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Sorry - Oh, I see, Many people have already been posting the errors. Since this is the case, I have been unable to locate the proginitor of the circuitry in any of the applications guides. I cannot find the professor or students who published this article. The editor appears to be "Bill Travis". Therefore, Bill, can you please provide us all with some references or sources? Possibly and IEEE paper reference, etc?
Kurt Kloesel - 2009-20-10 09:32:00 PDT -
Can anyone provide more references for th9is circuit? I am wondering whether the "no connection" between R26 and Q1 is a typographical error.
Kurt Kloesel - 2009-20-10 09:23:00 PDT -
Can anyone provide more references for th9is circuit? I am wondering whether the "no connection" between R26 and Q1 is a typographical error.
Kurt Kloesel - 2009-20-10 09:23:00 PDT -
Can anyone provide more references for th9is circuit? I am wondering whether the "no connection" between R26 and Q1 is a typographical error.
Kurt Kloesel - 2009-20-10 09:23:00 PDT -
Folks, Design Ideas are submitted by working engineers, and although we do our best to be accurate, errors do sometimes slip through. We can't always afford to go back and correct past mistakes because we're working hard on the next issue. We greatly appreciate discussions like this one because they help everyone get maximum value from Design Ideas. Thanks for participating!
Matthew Miller, EDN.com editor in chief - 2007-27-11 12:55:00 PST
