Multi stage amp

multistage amplifier

1. MULTISTAGE AMPLIFIERS, BIMOS TECHNOLOGY AND TUNNED AMPLIFIER Contents Multistage amplifier and cascade amplifier BIMOS circuits Tuned amplifier Single tuned amplifier Conclusion and References Prepared By S ARUN M.Tech Multistage and Tuned Amplifier 1

2. 2 Multistage Amplifier: If the voltage (or) power gain obtained from a single stage small signal amplifier is not sufficient for a practical application, more than one stage of amplification is used to achieve necessary voltage and power gain. Such an amplifier is called as a ‘ multistage amplifier ’. Cascaded Amplifier: A multistage amplifier using two (or) more single stage common emitter amplifier is called as ‘ cascaded amplifiers ’. Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

3. 3 BIMOS Circuits: BI – The bipolar technology uses npn and pnp bipolar junction transistors;  The bipolar transistors have a large transconductance than MOSFETs biased at the same current levels. MOS – The MOS technology uses NMOS and PMOS field effect transistors.  MOSFET circuits have an infinite input impedance , which indicates a zero input bias current. Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

4. 4 BIMOS Circuits: These advantages of the two technologies are exploited by combining bipolar and MOS transistors in the same integrated circuit. This technology is called ‘ BIMOS technology’ and it is used in digital circuit design and in analog circuits. Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

5. 5 BIMOS Cascode: A bipolar cascode circuit and corresponding BIMOS configuration is shown below: Bipolar c ascode configuration BIMOS cascode configuration Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

6. 6 Tuned Amplifiers: In order to obtain a large overall voltage gain, it is required to use a number of tuned amplifier stages in cascade. These cascaded tuned amplifiers are classified as : (i) Single tuned amplifiers (ii) Double tuned amplifiers (iii) Stagger tuned amplifiers Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

7. 7 Tuned Amplifiers: (i) Single tuned amplifiers – use one parallel resonant circuit as the load impedance in each stage and all the tuned circuits are tuned to the same frequency. (ii) Double tuned amplifiers – use two inductively coupled tuned circuits per stage, both the tuned circuits being tuned to the same frequency. (iii) Stagger tuned amplifiers – use a number of single tuned stages in cascade, the successive tuned circuits being tuned to slightly different frequencies. Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

8. 8 Single Tuned Amplifiers: Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

9. 9 Single Tuned Amplifiers: In the single tuned amplifier, the output across the tuned circuit is coupled to the next stage through the coupling capacitor Cc as shown below. Equivalent circuit of single tuned amplifier Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

10. 10 Single Tuned Amplifiers: Equivalent circuit of the output part of the tuned amplifier Simplified output circuit of the tuned amplifier Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

11. Single Tuned Amplifiers: Response of a tuned amplifier Prepared By S ARUN M.Tech Multistage and Tuned Amplifier

12. Conclusion From this detailed discussion of multistage amplifier is done. References Thomas L.Floyd, “Electronic devices” Conventional current version, Pearson prentice hall. Sedra and smith, “Microelectronic circuits”,7 th Ed., Oxford University Press. Robert L.Boylestad, “Electronic devices and circuit theory ” 12