An integrated 150 Vpp, 12 kV/ mu s class AB CRT-driving amplifier

Abstract

An integrated output amplifier with an output voltage swing of more than 150 V/sub pp/, a slew rate of 12 kV/ mu s, a large-signal bandwidth of 30 MHz, and a small-signal bandwidth exceeding 60 MHz is described. It is intended to drive the cathode of a cathode ray tube (CRT) in a projection television or a high-definition television (HDTV) set. The amplifier comprises a transadmittance stage followed by a feedback transimpedance amplifier. A zero in the feedback transfer allows the open-loop voltage gain of the transimpedance amplifier to have a -12-dB/octave slope at the unity loop-gain frequency. A zero in the transfer of the transadmittance stage results in a larger overall bandwidth than is possible in a conventional voltage-feedback configuration. The high-voltage DMOS technology which is used is based on a 10-mask bipolar process with double-sided p+ isolation and n+ collector diffusions. The 150-V/sub pp/ step response is shown. The rise and fall times are 11 and 12 ns, respectively, yielding slew rates of 13 and 12 kV/ mu s respectively. The overshoot is 12%. The small-signal (10 V/sub pp/) bandwidth, limited by the third pole of the transimpedance amplifier, exceeds 60 MHz. The large-signal (150-V/sub pp/) bandwidth, limited by slew rate, is 30 MHz. >