2W 音频放大器(英文)
this was one of the earliest circuits that i ever designed and built, in spring 1982. at that time i had only an analogue meter and a calculator to work with. although far from perfect, this amplifier does have a wide frequency response, low distortion, and is capable of driving an 8 ohm speaker to output levels of around 5 watts with slightly higher distortion. any power supply in the range 12 to 18 volts dc may be used.
circuit description
the amplifier operates in class ab mode; the single 470r preset resistor controls the quiescent current flowing through the bd139/140 complimentary output transistors. adjustment here, is a trade-off between low distortion and low quiescent current. typically, under quiescent conditions, standby current may be 15 ma rising to 150 ma with a 50 mv input signal. a simulated frequency response is shown below:
the circuit is dc biased so that the emitters of the bd139 and bd140 are at approximately half supply voltage, to allow for a maximum output voltage swing. all four transistors are direct coupled which ensures:-
(i) a good low frequency response
(ii) temperature and bias change stability.
the bc109c and 2n3906 operate in common emitter. this alone will provide a very high open loop gain. the output bd139/140 pair operate in emitter follower, meeting the requirements to drive low impedance speakers. overall gain is provided by the ratio of the 22k and 1k resistor. a heat sink on the bd139/140 pair is recommended but not essential, though the transistors will run 'hot' to the touch.
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2W 音频放大器(英文)
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circuit description
the amplifier operates in class ab mode; the single 470r preset resistor controls the quiescent current flowing through the bd139/140 complimentary output transistors. adjustment here, is a trade-off between low distortion and low quiescent current. typically, under quiescent conditions, standby current may be 15 ma rising to 150 ma with a 50 mv input signal. a simulated frequency response is shown below:
the circuit is dc biased so that the emitters of the bd139 and bd140 are at approximately half supply voltage, to allow for a maximum output voltage swing. all four transistors are direct coupled which ensures:-
(i) a good low frequency response
(ii) temperature and bias change stability.
the bc109c and 2n3906 operate in common emitter. this alone will provide a very high open loop gain. the output bd139/140 pair operate in emitter follower, meeting the requirements to drive low impedance speakers. overall gain is provided by the ratio of the 22k and 1k resistor. a heat sink on the bd139/140 pair is recommended but not essential, though the transistors will run 'hot' to the touch.
比特币界的神秘“鲸鱼whales”对市场的影响
继LG化学后,三星SDI也因ESS影响导致Q1利润环比减半
Arduino篇—多位数码管的应用
红米Note4强势登陆印度，Note4x离上市也不远了
阻抗匹配和史密斯图阻抗
2W 音频放大器(英文)
高大上5G技术相比4G，并没提升多少？5G CPE又是什么啥？
联合飞机参展无人机大会再现爆款，联合多方引领行业发展
一种为MCU提供稳定电压的高效电压转换电路
无人机侦测防御系统的作用：可实现监控取证
锁存器与触发器的概念及其区别
为什么无线通信行业需要O-RAN?
2019年的半导体行业发展不容乐观
日经新闻：村田制作所拟投资150亿日元扩大车载传感器产能
全新CORCOM DB系列电源接入滤波器
安全第一、常抓不懈，萝卜快跑组织开展安全培训
如何避免PLC程序卡死呢？
HIFI音响器材的使用维护注意事项
MAX7370 8×8键盘开关控制器,具有更高的防静电保护
中移动遭反竞争调查 或因定制机限制＂第二卡槽＂