Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
Advantages and Disadvantages of Tuned Amplifiers
Tuned Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• In tuned RF amplifiers, transistors are used at the frequencies nearer to their unity gain bandwidths (i.e. fT), to amplify a narrow band of high frequencies centred around a radio frequency.
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
Single tuned multistage amplifier circuit uses one parallel tuned circuit as a load in each stage with tuned circuits in all stages tuned to the same frequency. Fig. 8.10.19 shows a typical single tuned amplifier in CE configuration.
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• To amplify the selective range of frequencies, the resistive load, Rc is replaced by a tuned circuit. The tuned circuit is capable of amplifying a signal over a narrow band of frequencies centered at fr.
Differential Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• Higher the value of CMRR, better is the performance of differential amplifier. Hence in practice the efforts are always to improve the CMRR of the differential amplifier.
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• In the a.c. analysis, we will calculate the differential gain Ad, common mode gain Ac, input resistance Ri and the output resistance Ro of the differential amplifier circuit, using the h-parameters.
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• The d.c. analysis means to obtain the operating point values i.e. ICQ and VCEQ for the transistors used. The supply voltages are d.c. while the input signals are a.c., so d.c. equivalent circuit can be obtained simply by reducing the input a.c. signals to zero.
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• The differential amplifier, in the difference amplifier stage in the op-amp, can be used in four configurations
Equivalent circuit, Mode Operation
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• The transistorised differential amplifier basically uses the emitter biased circuits which are identical in characteristics.
Definition, Features, modes, Formula, Derivation, Solved Example Problems
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• The differential amplifier amplifies the difference between two input voltage signals. Hence it is also called difference amplifier.
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• A device which accepts an input signal and produces an output signal proportional to the input, is called an amplifier.
Equivalent circuit, Solved Example Problems | Multistage Amplifiers
Subject and UNIT: Electron Devices and Circuits: Unit IV: Multistage and Differential Amplifiers
• So far we have seen two basic amplifier technologies, the bipolar technology, which uses npn and pnp bipolar junction transistors, and the MOS technology, which uses NMOS and PMOS field effect transistors.