ELECTRONIC DEVICES. Assist. prof. Laura-Nicoleta IVANCIU, Ph.D. C8 Summing and differential amplifiers with OpAmp

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1 ELECTNIC DEVICES Assist. prof. Laura-Nicoleta IVANCIU, Ph.D. C8 Summing and differential amplifiers with pamp

2 C8 Summing and differential amplifs w/ pamp Contents Summing amplifiers with pamp Inerting summing amplifier Non-inerting summing amplifier Differential amplifiers with pamp ecap circuits with pamp Laura-Nicoleta IVANCIU, Electronic deices

3 C8 Summing and differential amplifs w/ pamp Types of amplifiers with pamp NI NI II Amplifier I ground non-inerting ground I inerting I I differential I, I ground summing, non-inerting ground I, I summing, inerting C7 C7 C8 Laura-Nicoleta IVANCIU, Electronic deices

4 C8 Summing and differential amplifs w/ pamp Summing amplifiers Inerting summing amplifier How can we compute? I + I elationship between resistors to obtain the aerage of input oltages: Laura-Nicoleta IVANCIU, Electronic deices

5 C8 Summing and differential amplifs w/ pamp Summing amplifiers Inerting summing amplifier Example +V PS -V PS a) ( i, i ) assuming op amp in the actie region. What is the application of the circuit? b) Considering i V, plot the VTC ( i ) for i [-5 V; 5 V]. What is the i range, so that the amplifier works in its actie region? c) Plot I (t), I (t) and (t) for I (t) sinωt [V], I (t) 0.5sinωt [V]. d) esize,,, so that -( i + i ). e) Modify the circuit, in order to obtain a non-inerting summing circuit, with i + i. Laura-Nicoleta IVANCIU, Electronic deices 5

6 C8 Summing and differential amplifs w/ pamp Summing amplifiers Non-inerting summing amplifier Laura-Nicoleta IVANCIU, Electronic deices + I + I elationship between resistors to hae? and Usually I I 6

7 7 Laura-Nicoleta IVANCIU, Electronic deices Differential amplifiers Differential amplifier C8 Summing and differential amplifs w/ pamp How can we compute? I I + +

8 8 Laura-Nicoleta IVANCIU, Electronic deices Differential amplifiers Differential amplifier C8 Summing and differential amplifs w/ pamp I + + I I I Superposition method

9 9 Laura-Nicoleta IVANCIU, Electronic deices Differential amplifiers Differential amplifier C8 Summing and differential amplifs w/ pamp I I + + If the goal is to amplify ( I - I ): + + ( ) I I The circuit amplifies the difference between the input oltages and rejects common mode signals. In practical situations: and For I I, 0. I noise + noise I + ) ( ) ( A A noise noise +

10 C8 Summing and differential amplifs w/ pamp Differential amplifiers Differential amplifier Superposition method Input resistance, seen by I I + Input resistance, seen by I I Laura-Nicoleta IVANCIU, Electronic deices 0

11 C8 Summing and differential amplifs w/ pamp Differential amplifiers Differential amplifier Example A sensor proides a ariable signal, i, with a dc component, V I. It is necessary to amplify the ariable signal, that carries information, 0 times. Design a differential amplifier for this requirement. Laura-Nicoleta IVANCIU, Electronic deices

12 C8 Summing and differential amplifs w/ pamp Differential amplifiers Differential amplifier Example ( t) I ( t) + + ( t) + + V EF ( VI + i ( t) ) VI Laura-Nicoleta IVANCIU, Electronic deices,5kω 5kΩ ( t) 0 ( t) o i

13 C8 Summing and differential amplifs w/ pamp Differential amplifiers Differential amplifier Standard instrumentation amplifier high i ery good common mode rejection ratio A and A: - high input resistance - set the gain A: - gain - conersion from two oltages ( and ) to a single oltage ( ) - additional rejection of the common mode Laura-Nicoleta IVANCIU, Electronic deices

14 Laura-Nicoleta IVANCIU, Electronic deices Differential amplifiers Differential amplifier C8 Summing and differential amplifs w/ pamp Standard instrumentation amplifier I I + I I + ( ) ( ) I I +

15 C8 Summing and differential amplifs w/ pamp Differential amplifiers Differential amplifier Integrated precision differential amplifiers AD8 Analog Deices Precision Instrumentation Amplifier A + (9. kω/ G ) MAX9, MAX95, MAX96, MAX97 Micropower, Single-Supply, ail-to-ail, Precision Instrumentation Amplifiers Maxim Integrated LT67 Linear Technology Common uses of instrumentation amplifiers: sensor readings for medical and industrial applications. Examples? Laura-Nicoleta IVANCIU, Electronic deices 5

16 C8 Summing and differential amplifs w/ pamp ecap circuits with pamp ecap circuits with pamp Gien a circuit with pamp, how can we tell whether the circuit is: inerting or non-inerting? a simple comparator, a hysteresis comparator, or an amplifier? What parameters do we compute, for each of the aboe? What can we tell about the output oltage? Laura-Nicoleta IVANCIU, Electronic deices 6

17 C8 Summing and differential amplifs w/ pamp ecap circuits with pamp ecap circuits with pamp Type of feedback No feedback Positie feedback Negatie feedback I goes to NI II NI II NI II Application We compute Simple comparator, non-inerting Simple comparator, V Th {V L ; V H } inerting Hysteresis comparator, non-inerting Hysteresis comparator, inerting Amplifier, non-inerting Amplifier, inerting V ThL V ThH {V L ; V H } A (V L ; V H ) Laura-Nicoleta IVANCIU, Electronic deices 7

18 C8 Summing and differential amplifs w/ pamp Summary Today s menu consisted of a fine selection of pamp circuits, such as: Summing amplifiers with pamp Inerting summing amplifier Non-inerting summing amplifier Differential amplifiers with pamp ecap circuits with pamp Next week: Applications with pamp - To do: Homework 7 Laura-Nicoleta IVANCIU, Electronic deices 8