Bridge Tied Load Amplifier: All of the power amplifiers already discussed have been single-ended (SE): meaning that they provide power to a load that has one terminal grounded and the other terminal connected to the amplifier output. These amplifiers either use a plus-minus supply with directly-coupled loads, or have a capacitor-coupled load and a single-polarity …
Audio Power Amplifier using IC Amplifier Driver: The LM391 integrated circuit Audio Power Amplifier using IC Amplifier Driver contains amplification and driver stages for controlling an externally-connected Class-AB output stage delivering 10 W to 100 W. The voltage gain and bandwidth are set by additional components. Internal circuitry is included for overload and thermal protection, …
Common Source Power Amplifier Using an Op Amp Driver Stage: Basic Circuit Operation – The Class-AB MOSFET Power Amplifier with OP Amp Driver Stage circuit in Fig. 18-45(a) consists of an operational amplifier (A1), two MOSFETs (Q3 and Q4), and several resistors. The op-amp together with resistors R4, R5, and R6 and capacitor C2 constitutes …
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BJT Power Amplifier with Op Amp Driver: BJT Power Amplifier with Op Amp Driver Circuit Operation – The Class-AB power shown in Fig. 18-39 uses an operational amplifier (A1) for the input stage. Resistors R4 and R5 together with the two diodes provide bias for the complementary emitter-follower BJT output stage There is 100% dC …
Complementary MOSFET Common Source Power Amplifier: Advantages of MOSFETs: Complementary MOSFET Common Source Power Amplifier have several advantages over power BJTs for large signal amplifier applications. One of the most important differences is that MOSFET transfer characteristics (ID/VGS) are more linear than IC/VBE characteristics for BJTs. This helps to minimize distortion in the output waveform. …
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BJT Power Amplifier with Differential Input Stages: Amplifier Circuit – The direct-coupled amplifier in Fig. 18-33 has a BJT Power Amplifier with Differential Input Stages constituted by transistors Q1 and Q2. It also has an intermediate stage (Q3) with a constant current load (Q4). Both pairs of output stage transistors (Q5 and Q7) and (Q6 …
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Power Supply Decoupling: Power Supply Decoupling – High-power amplifiers require high supply current levels, so unregulated power supplies are often employed to avoid the power wasted in a series regulator. The high ripple voltage that occurs with unregulated supplies can be amplified to appear at speaker outputs as very unpleasant power supply hunt Supply decoupling …
Output Current Limiting: Because the output transistors can be destroyed by excessive current flow, output current limiting circuits are often included in a power amplifier. Figure 18-27 shows the typical arrangement for a current limiting circuit. Emitter resistors RE2 and RE3 are each made up of two components (RA and RB), as illustrated. The Output …
Quasi Complementary Output Stage: The Quasi Complementary Output Stage was originally developed because complementary high-power transistors were not readily available. Despite the fact that such transistors are now available, the Quasi Complementary Output Stage circuit is still widely used. Consider the arrangement in Fig. 18-26. Q3 is a high-power npn transistor, and Q5 is a …
Darlington Connected Output Transistors: High-power transistors usually have low current gains, so relatively large base currents must flow into Q2 and Q3 to supply a high load current. This means that the quiescent current through Q1 must be large, and consequently resistor RC is small. The small value of RC keeps the amplifier voltage gain …