| 摘要 |
<p>The output signal of an npn long-tailed transistor pair amplifier stage (1) is referenced to a first power supply point (5). In order to transfer this signal to the input of a second npn stage (18) without using pnp transistors and without noise on the first supply point becoming superimposed on the signal, an intermediate stage (2) is provided. The intermediate stage comprises a current mirror (10) to the input and output of which are coupled the respective collectors of the pair transistors (3,4) via respective emitter followers (13,15) and respective resistors (14,16). The values of these resistors, the load resistors (6,7) of the pair transistors, and the current gains of the emitter followers and the current mirror are chosen such that any change in the potential on the output (17) of the intermediate stage (2) relative to a second power supply point (8) which would otherwise result from a change in the potential on the first supply point (5) relative to that on the second supply point is compensated for by a change in the mirror output current, thus producing changes in the currents through two of the resistors (7,16).</p> |
