Amplifier
AssigneeKoninklijke Philips Electronics N.V.
InventorWilliam Redman-White
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Abstract
A low noise amplifier with switchable gain settings comprises a cascoded emitter coupled pair (T1, T2, T5, T6; T3, T4, T7, T8) having a current diverter (T9, T10) which reduces the gain to an intermediate level in response to a control signal on terminals (8, 9). Further control signals on terminals (5, 10, 11, 12, 13) reduce the gain to a low level by introducing emitter degeneration (R3). To compensate for the increase in input impedance caused by the introduction of emitter degeneration feedback loops (C1, R8; C2, R9) are connected between the diversion path and the amplifier inputs.
Claims7
A low noise amplifier having switchable gain settings, the amplifier comprising a cascoded common emitter amplifier stage, a first arrangement for reducing the gain to an intermediate level, said arrangement including a signal diversion path which, when activated, causes a portion of the output signal to be diverted from the output and dumped, a second arrangement for reducing the gain to a low value, said second arrangement comprising means for increasing emitter degeneration and means for connecting a shunt feedback path from the diversion path to the input of the amplifier to reduce the increase in input impedance caused by the increase in emitter degeneration.
Dependencies are inferred from the claim text.