 Assistant Professor in Electronics and Telecommunication Engineering, WIT, Now today, I am going to explain you voltage to current converters Part 2. Learning outcomes of the session are at the end of the session, students will be able to draw and derive expressions for output current of V2I converters. And second is design of V2I converters. Contents of the session are V2I converters with offset. Second is derivation of load current and design of V2I converters. So first, V2I converter with offset. This is the circuit for V2I converter with an offset. Plus VCC minus VEE, operational amplifier. From inverting terminal, a resistance R span adjustable resistance is connected to the ground. This is a load. So load current I0 is controlled by VIN and V reference. So this is input. This is V reference. These are the resistances of 1 meg. Now this is the transfer curve for this V2I converter with offset. From the transfer curve, we see that if input voltage is VA, the load current is IA. And similarly, when input voltage is VB, load current is IB. Now from this transfer curve, we see that when the input voltage is 0, the load current is not 0. Means when input voltage is 0, this is the load current. So this is the offset. And due to this offset, we say this is V2I converter with offset. And offset depends on V reference. Now this is circuit. Now we proceed further for the derivation of the load current I0. For the given circuit, voltage at non-inverting terminal VX can be obtained by application of superposition theorem. So by superposition theorem, voltage at point X VX is equal to input voltage VIN into 1 meg upon 1 meg plus 1 meg. That is VIN by 2 plus V reference into 1 meg upon 1 meg plus 1 meg. That is V reference by 2. So this is equal to VIN plus V reference divided by 2. Considering ideal op-amp, voltage at inverting and non-inverting terminal should be equal. That is V plus equal to V minus. Now V minus is equal to V2 as shown in figure, which is equal to VX. And VX is obtained as VIN plus V reference by 2. Now, voltage across R-span, that is V2 is given by load current I0 multiplied by the resistance R-span. So V2 is equal to I0 into R-span, that is equal to VX. VIN plus V reference by 2. Simplifying further, we get I0 equal to VIN plus V reference upon 2 into R-span. Let this is equation number 1. Now, simplifying further, we get R-span is equal to VIN plus V reference upon 2 I0. Now from the transfer curve, we are having the two points, point A and point B. At point A, input voltage is VA and output current is IA. Similarly, at point B, input voltage is VB and the load current is IB. So substituting these values in the R-span, we get equation A and B as shown in figure. Simplifying further, we get 2 into R-span into IA equal to VA plus V reference. Let this is equation number C and 2 into R-span into IB equal to VB plus V reference. Let this is equation number D. Now, subtracting equations C from D, we get VB minus VA is equal to 2 R-span in the bracket IB minus IA. Simplifying further, we get R-span equal to VB minus VA upon 2 in the bracket IB minus IA. Let this is equation number 2. Then from equation number B, we can obtain the value of V reference. So solving equation number B, we get V reference equal to 2 into R-span into IB minus VB. Now, let this is equation number 3. Now, recall which type of V2I converters you have learned up till now and what are their circuits and design equations. So, we have learned four different V2I converters so first V2I converter is V2I converter with floating load and the design equation for this converter is I0 is equal to V in divided by R1 and RL is the load. Second V2I converter is V2I converter with grounded load as shown in figure and the design equation for this V2I converter is I0 is equal to V in divided by R. So, here R1 is equal to RF is equal to R and this is a load. So, all the resistances this is R R this is R this is R and this is a load and I0 is given by V in by R. Now, third type of V2I converter is V2I converter with offset. So, this is the circuit R-span this is load V in V reference plus VCC and minus VE and for the circuit these are the design equations R-span and this is V reference. So, R-span is given by VB minus VE upon 2 in the bracket IB minus IA and V reference to R-span into IB minus VB and the fourth V2I converter is differential V2I converter. So, this is E1 E2 and these are the resistances this is load and I0 is given by E2 minus E1 upon RS. Now, design of V2I converter basically consists of the two steps. First is selection of V2I converter from specifications of design problem and second is whatever V2I converter is selected in step number one that is design in detail. That is circuit and the design of components in the circuit. Now, let us take the design problem. Design V2I converter for the input voltage minus 5 volt to 10 volt and the required output current is 4 milliampere to 20 milliampere. From the given data transfer curve can be plotted as this is transfer curve means if input is VA is minus 5 volt at that time IA is 4 milliampere and input is 10 volt load current is 20 milliampere as shown in figure. So, this is given input and this is output current. Now, first is selection of circuit. So, we have selected V2I converter with offset because when input is 0 load current is not 0. Now, R-span is calculated by using this formula VB minus VA divided by 2 in the bracket IB minus IA substituting the values VB 10 volt VA minus 5 2 in the IB minus IA simplifying further we get R-span is equal to 468.7 ohm Now, 1 kilo ohm currentometer is used as R-span which is adjusted to the value 468.7 ohm and the V reference is calculated as V reference is equal to 2 into R-span into IB minus VB therefore, V reference is equal to substituting the value of R-span and IB we get V reference equal to 8.75 volt Now, this is the circuit Now, in this circuit operational amplifier 1 meg 1 meg V in V reference R-span and this is load Now, R-span is selected as a 1k pot as said earlier and V reference is 8.75 volt Now, next is selection of the operational amplifier So, 741 is selected as R-span Now, select VCC is equal to plus 12 minus VEE is equal to minus 12 volt Now, here reference of 8.75 volt is obtained as below from the potentiometer 1k potentiometer is used 1 end is connected to the ground and 1 end is connected to the plus 12 volt and by adjusting this part a few reference of these are references Thank you for watching this video