| 摘要 |
<p>An ultra-low power receiver and amplifier for receiving and amplifying data at a first frequency present as modulations of a carrier signal at a second, higher frequency has a photodiode (234) operable in the photovoltaic mode. A resonant filter (272) is connected across the photodiode; the filter shorts the photodiode at low freqencies and passes the frequency of the carrier signal and the frequency of the data signal. The output of the filter (272) leads to a first amplifier. The first amplifier has two stages (276, 278). Each stage is self-biasable as a Class A amplifier, and each stage shares a common, low, DC bias current. The output of the first amplifier leads to a second amplifier which amplifies only signals at the output of the first amplifier with a voltage which exceeds a predetermined voltage. The output of the second amplifier leads to a further filter which filters signals at the carrier frequency from the output while passing signals at the data frequency. The amplifier is particularly useful in devices (such as parking meters) powered by a battery.</p> |
