1. Amplifier An amplifier increases the strength of an electrical signal. Symbol: Type:analogue process device Amplifiers are used in: 1.radios and TV’s 2.intercoms 3.baby alarms Amplifiers increase the amplitude of the electrical signal. FREQUENCY is NOT CHANGED.

2. Voltage Gain ViVi VoVo LARGER AMPLITUDE FREQUENCY stays the SAME input signal output signal

3. The size of the voltage gain is given by: x ÷ VoVo V gain ViVi QuantityUnit Output Voltage ( V o ) Voltage Gain ( V gain ) Input Voltage ( V i ) Volts ( V ) NO UNIT Volts ( V ) The voltage gain of an amplifier is the number that the input voltage is multiplied by to give the output voltage.

4. Example 1 An amplifier turns a 20 mV signal into 300 mV signal. Calculate the voltage gain of the amplifier. ** NO UNIT **

5. Example 2 An amplifier with a voltage gain of 80 is supplied with an input voltage of 7 mV. Calculate the output voltage.

6. Power Gain The power gain of an amplifier is given by: x ÷ PoPo P gain PiPi QuantityUnit Output Power ( P o ) Power Gain ( P gain ) Input Power ( P i ) Watts ( W ) NO UNIT Watts ( W )

7. There are also 3 formulae for electrical power we met in the topic “Using Electricity” x ÷ P I V x ÷ P I2I2 R x ÷ V2V2 P R

8. Example 1 An amplifier has an output power of 50 W. The input voltage is 12 V and the input resistance is 1 kΩ. Calculate:(a)the input power (b)the power gain. (CREDIT) (a)

9. (b) ** NO UNIT **

10. Yellow Book Page 56 Analogue Processes – Q63 Voltage Gain –Q67, Q70 Page 57 Power, Voltage, Resistance – Q72, Q73 Power Gain – Q76

11. Yellow Book Mixed Problems on Amplifiers Q80, Q84, Q86, Q88