Subject : Analog Electronics Branch : Electrical – A Semestar : 3rd Guide by : Dhanush Sir Hardik Sir

Inverting & non- Inverting amplifier

Prepared by : 1. Sandip Baldha. 130940109001 2. Keval Chandarana. 130940109008 3. Vishal Domadiya. 130940109018 4. Ronak Kakadiya. 130940109033 5. Chetan katariya. 130940109038 5. Chetan katariya. 130940109038

Differential Amplifier Model: Basic Represented by: A = open-circuit voltage gain vid = (v+-v-) = differential input signal voltage Rid = amplifier input resistance Ro = amplifier output resistance The signal developed at the amplifier output is in phase with the voltage applied at the + input (non-inverting) terminal and 180° out of phase with that applied at the - input (inverting) terminal.

Ideal Operational Amplifier The “ideal” op amp is a special case of the ideal differential amplifier with infinite gain, infinite Rid and zero Ro . and If A is infinite, vid is zero for any finite output voltage. Infinite input resistance Rid forces input currents i+ and i- to be zero. The ideal op amp operates with the following assumptions: It has infinite common-mode rejection, power supply rejection, open- loop bandwidth, output voltage range, output current capability and slew rate It also has zero output resistance, input-bias currents, input-offset current, and input-offset voltage.

The Inverting Amplifier: Configuration The positive input is grounded. A “feedback network” composed of resistors R1 and R2 is connected between the inverting input, signal source and amplifier output node, respectively.

Inverting Amplifier:Voltage Gain The negative voltage gain implies that there is a 1800 phase shift between both dc and sinusoidal input and output signals. The gain magnitude can be greater than 1 if R2 < R1 The gain magnitude can be less than 1 if R1 < R2 The inverting input of the op amp is at ground potential (although it is not connected directly to ground) and is said to be at virtual ground. But is= i2 and v- = 0 (since vid= v+ - v-= 0) and

Inverting Amplifier: Input and Output Resistances Rout is found by applying a test current (or voltage) source to the amplifier output and determining the voltage (or current) after turning off all independent sources. Hence, vs = 0 But i1=i2 Since v- = 0, i1=0. Therefore vx = 0 irrespective of the value of ix .

Inverting Amplifier: Example Problem: Design an inverting amplifier Given Data: Av= 20 dB, Rin = 20kW, Assumptions: Ideal op amp Analysis: Input resistance is controlled by R1 and voltage gain is set by R2 / R1. and Av = -100 A minus sign is added since the amplifier is inverting.

The Non-inverting Amplifier: Configuration The input signal is applied to the non-inverting input terminal. A portion of the output signal is fed back to the negative input terminal. Analysis is done by relating the voltage at v1 to input voltage vs and output voltage vo .

Non-inverting Amplifier: Voltage Gain, Input Resistance and Output Resistance Since i-=0 and But vid =0 Since i+=0 Rout is found by applying a test current source to the amplifier output after setting vs = 0. It is identical to the output resistance of the inverting amplifier i.e. Rout = 0.

The Difference Amplifier Since v-= v+ For R2= R1 This circuit is also called a differential amplifier, since it amplifies the difference between the input signals. Rin2 is series combination of R1 and R2 because i+ is zero. For v2=0, Rin1= R1, as the circuit reduces to an inverting amplifier. For general case, i1 is a function of both v1 and v2. Also,

Difference Amplifier: Example Problem: Determine vo Given Data: R1= 10kW, R2 =100kW, v1=5 V, v2=3 V Assumptions: Ideal op amp. Hence, v-= v+ and i-= i+= 0. Analysis: Using dc values, Here Adm is called the “differential mode voltage gain” of the difference amplifier.