Transistors are used for current sources. Base drive for these transistors is derived from the main power supply VA, so that their collector current is proportional to the rail voltage. This feature holds the voltage on the cliff-amp collectors close to VA/2. The sensitivity of Iq to VA is about 3.4 mA/volt when VB is held constant; the sensitivity of Iq to VB is -15 mA/volt when VA is held constant. In a practical amplifier with a non-regulated supply, variations in power output will cause fluctuations in VA, but will not affect VB; therefore, having Iq increase slightly with power output will tend to compensate for the 3.4 mA/volt IqVa sensitivity. In the case of line voltage variations, since VA is about five times VB, the sensitivities tend to cancel, leaving a net sensitivity of about 2 mA/volt.
200W Hybrid Audio Amplifier Circuit - c onnecting two TDA2030 thru cheap power transistors we can create a amplifier wich can deliver a higher power. With the components value from the schematic the total amplifier gain is 32 dB. The speaker can be 2 ohm instead of 4 ohm if we use the TIP transistors. TDA 2030 is produced by SGS Ates and is a complete audio amplifier. AB class of the final amplifier cand deliver up to 14W on 4 ohm at a +-14V power supply. With a proper designed power supply this audio amplifier can output 200W. Active components: IC1, Ic2 TDA 2030 T1, T3 = BD 250, TIP 36 T2,T4 = BD 249, TIP 35 D1 … D4 = 1N4001 200W Hybrid Audio Amplifier Circuit

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