2W 音频放大器(英文)
出处:boy4477 发布于:2007-09-22 00:00:00 | 3369 次阅读
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.
版权与免责声明
凡本网注明“出处:维库电子市场网”的所有作品,版权均属于维库电子市场网,转载请必须注明维库电子市场网,https://www.dzsc.com,违反者本网将追究相关法律责任。
本网转载并注明自其它出处的作品,目的在于传递更多信息,并不代表本网赞同其观点或证实其内容的真实性,不承担此类作品侵权行为的直接责任及连带责任。其他媒体、网站或个人从本网转载时,必须保留本网注明的作品出处,并自负版权等法律责任。
如涉及作品内容、版权等问题,请在作品发表之日起一周内与本网联系,否则视为放弃相关权利。