 session on Wendridge oscillator and misses by the Higulkarni. Learning outcomes are at the end of session students will be able to analyze the Wendridge oscillator circuit. Contents are like this basic principle for the Wendridge oscillator as it is a part classification of RC oscillator it consists of the network two stage amplifier which provides 360 degree phase shift. Next output of this two stage amplifier is given to the bridge circuit which consists of RC network that is series and parallel combination of RC and two more RC network forming a Wendridge circuit which is used to stabilize the output of oscillator. This further is given to the input of two stage amplifier. So, here total phase shift of 360 degree is obtained with this two stage amplifier and will be maintained such that sustained oscillations can be obtained. So, Wendridge oscillator is a circuit which provides you the sine waves at the output with the frequency range of 20 hertz to 20 kilohertz. So, it is also called as type of audio oscillator. So, this is the basic block diagram of Wendridge oscillator circuit where total phase shift is obtained through the two stages of amplifier and bridge circuit is used to just stabilize the output. Figure 2 shows the circuit diagram for Wendridge oscillator circuit. Due to the thermal noise of the active and passive elements, noise gets generated in the circuit and that gets amplified and further given to the transistor Q2 which amplifies your signal as well as phase shift it with the 180 degree. So, this 180 degree plus 180 degree phase shift signal that is which is in phase with the input is provided to the bridge circuit. In the bridge circuit you can observe this is your R1 C1 series combination and R2 C2 parallel combination which gives the positive feedback nothing but regenerative effect and R4 resistor will provide you degenerative effect that is negative feedback which gives the amplitude stability to the output. So, this bridge gets balanced at particular condition and then you are providing this signal through this circuit and that is at the base of transistor Q1. So, we can say here Vf is given to transistor Q1 and V0 is given to the bridge circuit. So, here output of Q2 is feedback to the bridge circuit, R4 provides the degenerative effect, R2 provides regenerative effect which is in parallel combination with C2. C1 and C2 variations will give you the change in the value of the frequency. So, it will decide the value of frequency whereas R1 and R2 variations will decide the change in the range of frequency. Now, we will see the expression for gain and frequency of oscillation. So, here Vendridge oscillator circuit as R1 and R2 are connected in series. We can write it as R plus 1 by j omega C whereas parallel combination can be written as Z equal to R by 1 plus j omega C R. So, when your bridge gets balanced then its arm resistance will be equal to R3 divided by R1 plus 1 by j omega C1. This is equal to R4 divided by parallel combination of R2 and C2 that is nothing but R2 by 1 plus j omega C2 R2. After simplification or after cross multiplication and the simplification of the equation by separating the real and imaginary part you will get the equation like this R2 R3 minus R1 R4 minus R2 R4 C2 divided by C1 plus now the imaginary part that is j R4 by omega C1 minus R2 C2 R1 R4 omega. This is imaginary part of the equation that is R4 by omega C1 minus R2 C2 omega R1 R4. Now, when you equate this imaginary part to 0 you will obtain the frequency of oscillations for the Wengerges later circuit. So, here R4 by omega C1 equal to R2 C2 R1 R4 omega. So, we can write here omega square equal to R4 by R2 C2 R1 R4. So, we can say here the value of so, you have to take the C1 also to this side. So, you will get this omega C1 here. So, only omega over here. So, it will be C1. So, if you consider the values of resistance that is R1 equal to R2 equal to R and C1 equal to C2 equal to C then all these values will become same. So, you can write omega square equal to R square C square. Therefore, omega is what 2 pi f. So, f can be written as 1 by 2 pi Rc 1 by 2 pi Rc gain. How to obtain the value of gain? So, you can see here again look at the bridge circuit here as you know Vf is there at the base of Q1 and V0 is applied through C3 to the bridge circuit. So, as you know Z1 is the series combination of register and capacitor. So, it will be R1 minus j Xe1. Z2 is parallel combination. So, it will be minus j R2 Xe2 by R2 minus and Vf equal to V0 into Z2 by Z1 Z2 by Z1 plus Z2. So, beta is nothing but ratio of Z2 by Z1 plus Z2. So, here Z2 is minus j R2 by Xe2 divided by Z1 plus Z2. So, that is Z1 is R1 minus j Xe1 plus this is Z1 plus Z2 that is minus j R2 Xe2 by R2 minus j Xe2. So, here R2 minus j Xe2. So, when you simplify this equation and further you assume R1 equal to R2 equal to R and Xe1 equal to Xe2 equal to Xe. So, you will come across the equation for beta like this that is 1 divided by 3 plus j into bracket R by Xe minus Xe by R. Simply separate out the real and imaginary part over here and see here you will beta will be 1 by 3 plus j into bracket R by Xe minus Xe by R. So, if you consider the real part over here. So, you will get beta equal to 1 by 3 and the condition for sustained oscillation is Av beta must be greater than 1. So, Av should be greater than or equal to 1 upon beta 1 upon beta is 3. So, we can say here when voltage gain of 2 stages of amplifier is greater than 3 then and then sustained oscillations can be obtained. So, this is the condition for gain for Wendridge oscillator circuit. Now, recall a Wendridge oscillator circuit generates the oscillation only if gain of 2 stage amplifier greater than 3. Yes, this is the correct answer. Now, why is the negative feedback provided in the Wendridge oscillator circuit? Through the registers you are providing the negative feedback and answer is to stabilize the amplitude of output. Applications of Wendridge oscillator as it is providing the 0 degree phase shift through the bridge circuit. So, it is used for generating the 0 degree stable oscillator related circuitry. It is very good for the audios applications where stability of frequency and amplitude is obtained through the 2 stages of amplifier and the bridge circuit. It is used for the distortion testing in power amplifiers. Also used for excitation for AC bridge. It is very useful to fabricate the pure tune because it is a very special type of audio oscillator circuit. As we are using the bridge circuit over here it is used to measure the audio frequency of signal. References are like this. Thank you.