| 摘要 |
An analog amplifier is specified, in particular an AF amplifier for broadcast receivers, which has two inverting operational amplifiers (20, 21) connected in series. The negative feedback loops of the operational amplifiers (20, 21) are controlled by adjustment of the resistance ratio which determines the gain, in such a way that the overall gain can be adjusted in equal-increment steps. The amplifier with actively controlled gain has a significantly improved signal-to-noise ratio compared with AF amplifiers with passive volume control (Fig. 1). <IMAGE>
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