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瞬态互调失真是影响OCL电路性能的重要原因,降低大环路负反馈的深度、取消滞后补偿电容是减小瞬态互调失真的重要途径之一,而这一切都要求首先减小OCL电路的开环失真。本文想就这方面谈一点粗浅的看法。最后,介绍一个开环失真小于0.3％的OCL电路以及部分实测指标。该电路的其它特点是:大环路负反馈较浅(10dB);完全不用滞后补偿;末级大功率管是两只NPN型硅管且不需要配对;晶体管几乎不用筛选(倘若筛选,则对电路的改进,对开环失真指标还很有希望进一步提高,那时有可能完全不用大环路负反馈);末级工作点是自动稳定的,无信号时电流小于40mA。下面先分析典型OCL电路开环失真产生的原因,然后再探讨解决办法。
Transient intermodulation distortion is an important factor affecting the performance of OCL circuits. Decreasing the depth of large loop negative feedback and canceling lagging compensation capacitors are one of the important ways to reduce the transient intermodulation distortion. All this requires that the OCL Circuit open loop distortion. This article would like to talk a little superficial view on this. Finally, we introduce an OCL circuit with open-loop distortion of less than 0.3% and some measured data. The circuit’s other features are: large loop negative feedback shallow (10dB); no hysteresis compensation; the end of the high-power tube is two NPN-type silicon tube and does not require pairing; transistors almost without screening (if the screening, the Circuit improvement, the open-loop distortion index is still very much hope to further improve, then there may not be a big loop negative feedback); the final stage of the working point is automatically stable, no signal current less than 40mA. The following analysis of the typical OCL circuit open loop distortion causes, and then explore the solution.