Cowect To

most posnrvt

^ DC SUPPLY VOLTAGE

Fig. 3. Schematic diagram of the RCA OA

3005 integrated circuit rf amplifier.

and Q3 are functioning as a common-emitter common-base pair which is better known as a cascode configuration. This configuration has a very distinct advantage because it considerably reduces the internal feedback as compared to a single transistor. The fact that the internal feedback is extremely low means that these circuits (the MC 1550 and CA 3005) are very stable, and you wont have to concern yourself with neutralizing,

Another performance advantage is the AGC capability of these integrated circuit devices as compared to a single transistor. The application of an AGC voltage to Q2 has negligible effect on the operation of Ql, hence, the input characteristics of Ql remain constant. Ihus, there is no detuning of the tuned input circuit with changes in the AGC voltage.

Both the RCA and Motorola circuits can be operated as a differential amplifier with minor external modifications in the wiring. Some of the options of using the cascode configuration or the differential configuration will be covered later.

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Integrated Circuit Agc

Fig. 4. Typical 50-60 MHz tuned amplifier. Gain Is 30 dB with 0 volts AGC and bandwidth is 5

MHz,

Fig- 2. Schematic diagram And photograph of the Motorola MC 1550, Terminal numbers refer to leads on TO-5 type package.

Fig. 4. Typical 50-60 MHz tuned amplifier. Gain Is 30 dB with 0 volts AGC and bandwidth is 5

MHz,

Tuned Amplifier With

substrate

Fig- 2. Schematic diagram And photograph of the Motorola MC 1550, Terminal numbers refer to leads on TO-5 type package.

substrate

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out v both windings nq<36e on t-12-z core

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out v both windings nq<36e on t-12-z core

A diagram of the die for the Motorola MC 1550 is shown in Fig. 2. The tiny sill-con chip contains the three transistors, four resistors and the diode. Resistors Ri and R 2 bias Di, and also provide a base voltage for Q3. The other resistors Rn and R( broaden the AGC voltage range from the previously mentioned 114 mV to about 0.86 volts to reduce susceptibility to noise interference.

The schematic diagram for the RCA CA

0 0

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