| 摘要 |
<p>A programmable gain amplifier including first (10) and second (15) gain elements are connected by an impedance selector (14B) which allows programmability of the gain of both gain elements. The impedance selector (14B) is connected in series with the output of the first gain element (10). The impedance selector (14B) places an impedance in the feedback path of the first gain element (10) or the input path of the second gain element (15). Errors introduced in the signal path due to the switches (S1...SN) are attenuated by the open loop gain of the first gain element. The gain may be equally divided between both stages of the amplifier to allow for optimum bandwidth. Optimum noise performance may be obtained by placing most of the gain in the first stage. An instrumentation amplifier may also be made which further includes a third gain element (18) connected to the gain element with a second impedance selector (19) in a manner similar to the connection of the first gain element (10) to the second gain element (15).</p> |
