Elektronika (TKE 4012)

Transcription

1 Operational Amplifier & aplikasinya Elektronika (TKE 40) Eka Maulana maulana.lecture.ub.ac.id

2 Op Amp Op Amp is short for operational amplifier Amplifiers proide gains in oltage or current Op amps can conert current to oltage Simbol Op Amp High Supply (+) Non-inerting input Inerting input + Output Low Supply (-) Ground

3 Applications of Op Amps Op amps can be configured in many different ways using resistors and other components Most configurations use feedback Op amps can proide a buffer between two circuits Op amps can be used to implement integrators and differentiators Lowpass and bandpass filters

4 Aplikasi Op-amp Komparator Penguat Non-inerting Penguat Inerting Penguat penjumlah Voltage follower Conerter Tegangan ke Arus Integrator & Diferensiator Penguat diferensial Penguat instrumentasi Penguat histerisis

5 The Op Amp Model An operational amplifier is modeled as a oltage-controlled oltage source. Non-inerting input + + o in + Inerting input A( + ) Voltage controlled oltage source

6 Typical s. Ideal Op Amps Typical Op Amp: The input resistance (impedance) in is ery large (practically infinite). The oltage gain A is ery large (practically infinite). Ideal Op Amp: The input resistance is infinite. The gain is infinite. The op amp is in a negatie feedback configuration.

7 Consequences of the Ideal Infinite input resistance means the current into the inerting () input is zero: i = 0 Infinite gain means the difference between + and is zero: + = 0

8 Typical Op Amp Parameters Parameter Variable Typical anges Open-Loop Voltage Gain Ideal Values A 0 5 to 0 8 Input esistance Output esistance i 0 5 to 0 3 W W o 0 to 00 W 0 W Supply Voltage Vcc/V + -Vcc/V - 5 to 30 V -30V to 0V N/A N/A

9 Symbols for Ideal and eal Op Amps OpAmp ua74 LM34 LM

10 Voltage Transfer Characteristic ange where we operate the op amp as an amplifier. d Vcc(+) V V + V O V d = V -V Vcc(-)

11 Example #: Voltage Comparator Vcc(+) V V + Vo V d = V -V Vcc(-) When V d is larger than 0V, Vo = Vcc (+). When V d is smaller than 0V, Vo = Vcc (-). When V d is equal to 0V, Vo = 0V.

12 Penguat Inerting Basic V + + in + V out

13 Soling the Amplifier Circuit Apply KCL at the inerting () input: V out i 0 V in i i i V i V in V V in i + i + i =0 i V out V V out

14 Sole for V out From KCL V i in V in i V out i V 0 0 out 0 Thus, the amplifier gain is V V out in

15 ecap The ideal op-amp model leads to the following conditions: i = 0 = i + + = These conditions are used, along with KCL and other analysis techniques (e.g., nodal), to sole for the output oltage in terms of the input(s) Lect8 EEE 0 5

16 Penguat Non-inerting + + in + out

17 KCL at the Inerting Input + i 0 in + i i i + out i i out out in in

18 Sole for out i in out i out in i 0 in 0 Hence, the non-inerting amplifier has a gained output (> unity) relatie to the resistance ratio

19 angkaian Penjumlah f out

20 KCL at the Inerting Input i i i f f i 0 + i i out i f out f out f i

21 Sole for out So, the mixer circuit output is a (negatie) combination of the input oltages 0 0 i i i i f f out f out f

22 ac coupled inerting amplifier C C in f unity A V = - f = + L out f c = p C f c = pl C

23 Adjustable bandwidth in out A B = + - f = Bf unity f

24 ac coupled noninerting amplifier C C in 3 L out B dc = f c3 = p C 3 C 3

25 JFET controlled inerter/noninerter in out 0 V V GS(off)

26 Adjustable gain of ± in out

27 Phase shifter out in C t f = - arctan pcf f

28 Differential amplifier in(cm) in out A V = - in(cm) CM limiting factors are the op amp itself and the tolerance of the resistors. Ideally: = = D ± < A CM < ±4 D

29 Wheatstone bridge +V 3 out 4 Transducer

30 Wheatstone bridge The differential output signal is small. The common-mode output signal is large. Differential amplifiers are a good match. Transducers conert nonelectrical quantities into an electrical quantity such as resistance: examples: photoresistor, thermistor, strain gage

31 Instrumentation amplifiers Differential amplifiers optimized for dc performance Large differential oltage gain High CM Low input offsets Low temperature drift High input impedance

32 in(cm) Instrumentation amplifier in G out in(cm) A V = - G + A CM = ± D

33 Monolithic instrumentation amplifiers Use laser-trimmed resistors for high performance. esistor G is external and is selected to set the differential gain. esistor G can be split into two deices for guard driing (bootstrapping the cable shield to the common-mode potential).

34 Guard driing G G Instrumentation amplifier out Guard oltage (common-mode oltage)

35 Summing amp with inerting and noninerting inputs F out

36 D/A conerter 3 4 out 8 in 0 8 N = 4 out = -( ) Possible combinations = N = 4 = 6

37 Unidirectional current booster +V CC in 74 b dc = 00 L out I max = b dc I SC = 00(5 ma) =.5 A

38 Bidirectional current booster +V CC in L out -V EE

39 AGC circuit in 5 Voltage-controlled resistance 6 out +V AGC 3 4 As the signal leel increases, V AGC goes more positie. As the JFET r ds drops, the input signal is attenuated. -V EE

40 Single-supply inerting amplifier C +V CC C in C 3 L out +V CC