Aplikasi Op amp

Pertemuan ke 10Kuliah Elektronika Dasar

Prodi Teknik ElektroJTETI-UGMMei 2010

Arah arus ?

INV and SUMMING

V to I

Buktikan !

V to I

INTEGRATORI1 = (Vi - V)/R1

I2 =

set I1 = I2,

(Vi - V)/R1 =

but V- = V+ = 0

Vi/R1 =

Solve for Vo

Output is the integral of input signal. CR1 is the time constant

I1

I2

dt

VVdC o

dt

VVdC o

dt

dVC o

dtvCR

v io1

1

Bila vi konstan maka tCR

vv i

10 Linier

OUTPUT INTEGRATOR(dengan tegangan masukan tetap)

tCR

vv i

10

-VCC

t

v0

Pembangkit gelombang gigi gergaji

I1

I2

Saklar ditutup sebelum opamp jenuh,kemudian langsung buka lagi

-VCC

t

v0

Saat saklar ditutup

APLIKASI

• Pembangkitan bentuk gelombang

• Kemiringan tergantung besarnya RC

tCR

vv i

10

DIFERENSIATOR

Output is the differential of input signal. CR is the time constant

dt

VdC

dt

VVdCI inin

1

Vo

I1

I2

–

+Vin+

–

C

R

+–

R

V

dt

dVC in 0

R

V

R

VVI 00

2

dt

dVRCV in0

Bila input konstan maka tegangan output = nol

Aplikasi diferensiator

• Kelengkungan tergantung besarnya RC

Integrator

+

~

R

Vin

Vo

C

Tegangan Input

Tegangan Output

Ref:080114HKN Operational Amplifier 16

Tegangan Output IntegratorExample:

(a) Determine the rate of changeof the output voltage.

(b) Draw the output waveform.

Solution:

+

R

VoVi

0+5V

10 k

0.01FC

Vo(max)=10 V

100s

(a) Rate of change of the output voltage

smV/

F k

V

50

)01.0)(10(

5

RC

V

t

V io

(b) In 100 s, the voltage decrease

VμssmV/ 5)100)(50( oV

0+5V

0

-5V

-10V

Vi

Vo

Differentiator

18

Astable Multivibrator or Relaxation Oscillator

Circuit Output waveform

19

Equations for Astable Multivibrator

21

2

21

2 ;RR

RVV

RR

RVV sat

LTsat

UT

1

2121

2ln2

R

RRttT

Assuming|+Vsat| = |-Vsat|

If R2 is chosen to be 0.86R1, then T = 2RfC and

where = RfC

CRf

f2

1

Function Generator - Build your own!Ever wonder how turning a knob on a function generator (which is a variable resistor) can change frequencies? This circuit employs the last two - the integrator and the Schmitt trigger. There is also another old friend - the transistor switch. Lets look at how this circuit works.

First look at the Schmitt trigger part. When does it change? Look at the resistors in the +feedback - this is not the same as our example.

Vin

Function Generator - Build your own! (2)Now look at the first part. When the output is “HI”, meaning close to the power supply voltage, the transistor is OFF, so if effectively is not there. Then if the cap has more that Vin/2 across it, it will discharge through the 100k resistor. If the output is low, the inverting input is effectively grounded through a resistor and it will charge the cap. Changing Vin will change the charge/discharge rate.

Vin