Keywords: power amplification, gallstone mix
Author: Xu Yingming
The whole-line coupling mixed power is made by the author, and the tube and transistor are organically integrated together. Among them, the bipolar transistors only starts constant current and excessive effects, no current gain, effectively avoids the vital harmonic distortion, under the 10V output, almost a straight line from 10 Hz ~ 110kHz.
First, the principle introduction to the tube VE1, VE2 and transistors V5, V6 constitute the common-pellet-based voltage amplifier, V3, V4 is a constant current source, but no longer the load of VE1, VE2, but with V5, V6 will VE1, VE2 caused by the input signal change direction, V1, V2 constant current source load is V8, V9, and V9 collector pair, one 200kΩ resistor is to improve the open-loop frequency, V8 collector and negative power supply The alternating capacitor shorts the AC signal, and the V9 no longer contributes the gain, which has become a pure load and a zero potential operating point of the V8 to stabilize the output stage to suppress common mode signals. Thus, the current gain of the entire voltage amplifier is completed by tubes, V5, V6 has no current gain, and the bipolar tube in the channel does not have a wonderful harmonic, maintaining electronic pipe tone. Since the output internal resistance of the voltage amplification is very high, VE3, VE4 uses the tube parallel positive output to form buffering and end-level promotion level, with very low internal resistance and larger current drive the final two-pair of field effect tubes (only Picture a pair). In order to make this amplifying circuit has perfect "courage", the output stage uses the power field effect tube close to the tube audio, and the static current bias tube between the two gates of the end-stage tube also uses a small power VMOS tube. .
Second, component selection and debug V5, V6, V7 are preferably used in medium power tubes greater than 180V with high frequency, small current, withstand voltage. 4 red luminescent diodes do regulator tubes, and their pipe pressure drop is around 1.9V to 2V. Each of the end-level has been used with two pairs of K1529, J200. This circuit uses two transformers, one of which is dedicated to filament and delay circuitry.
Production and debug: After checking correctly, the end-level power tube is not installed. The output is connected to a 10kΩ resistor for a false load. After power-on, about 20s ~ 30s after the relay, the main circuit is powered on (such as the delay time is not suitable can change the capacity of 4700μF capacitor). . The lowermost static current bias tube is adjusted to the maximum value, the variable resistance between the V8, V9 two emitters, so that the tube Ve3, VE4 cathode potential can float up and down, and finally set to the OV. At this time, check the static currents of the endless level should be substantially consistent with the values in the figure, otherwise the electrode resistance value of the respective constant flow tube should be adjusted. After no problem, the final power tube (when welding is preparation), the output end fake load is replaced by 10 Ω to 10Ω ~ 20Ω power resistance, after power-on, adjust the adjustable resistance between V8 and V9 The output is zero potential, and the variable resistance between the static bias tube gate source pole is slowly generated by the post-stage, pay attention to the start of the beginning, and then adjust to 200 mA. Note that the end-class VMOS tube is less than 150 mA. Don't forget to re-adjust it after a few days.
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