Audio amplifier made by discrete elements

Projekt ovog rada je projektirati i realizirati višestupanjsko asimetrično napajano audio pojačalo pomoću diskretnih elemenata. Pojačalo treba imati naponsko pojačanje od 20 dB, donju graničnu frekvenciju od 1 Hz, gornju graničnu frekvenciju od 20 kHz te napon napajanja 30 V. Navedeno pojačalo se projektira u tri stupnja pojačanja. Prvi stupanj pojačala se izvodi bipolarnim diferencijskim pojačalom s strujnim izvorom. Drugi stupanj pojačala se sastoji od kaskodnog spoja dva PNP bipolarna tranzistora. Treći stupanj se izvodi s MOSFET tranzistorom u spoju zajedničkog odvoda koji se odlikuje malim izlaznim otporom. Na ulazu sklopa se postavlja CR i RC mreža kojom se definiraju gornja i donja granična frekvencija pojačala. Regulacija pojačanja i smanjenje izobličenja se rješava negativnom povratnom vezom. Negativna povratna veza poboljšava linearnost pojačala, ali utječe na izlazni, ulazni otpor te proširenje frekvencijskog pojasa pojačala.The project of this study is to design and implement a multistage asymmetrically powered audio amplifier using discrete elements. The amplifier should have a voltage gain of 20 dB, the lower cut-off frequency of 1 Hz, the upper cut-off frequency of 20 kHz and 30 V supply voltage. This amplifier is designed in three gain stages. The first stage of the amplifier is designed with bipolar differential amplifier with a current source. The second stage of the amplifier consists of two PNP bipolar transistors made with cascode circuit. The third stage is carried out with a MOSFET transistor in a common junction leakage, which is characterized by low output resistance. CR and RC network is placed at the entrance of the assembly, which defines upper and lower cut-off frequency of the amplifier. Gain control and reduction of distortion can be offset by the negative feedback. Negative feedback improves the linearity of the amplifier, but it affects the output resistance and entry resistance. It also causes expansion of the frequency range of the amplifier