Download Voltage Regulator

Study of Voltage Regulator
LAB:- CEII (SEM V EXTC)
Aim and Apparatus
Aim : Design and study of voltage regulator
Apparatus : IC 723, Resistors, Capacitors, Unregulated Power supply,
Multimeter.
fig 1
LAB:- CEII (SEM V EXTC)
Theory
• IC 723 has unregulated dc supply at input between 11.5 V to 40 V. It
can withstand maximum load current of 150 mA. Internal power
dissipation is about 800 mW. It has low temperature and high ripple
rejection. The output voltage can be adjusted between 2 V to 37 V.
The pin configuration of IC 723 is shown in fig 1.
Reference : http://www.ti.com/lit/ds/symlink/lm723.pdf
LAB:- CEII (SEM V EXTC)
The functional block diagram of IC 723 consists
of a reference generating block. The main
function of this block is to generate a fixed
reference voltage internally with the help of
zener diode. The error amplifier is a high gain
differential amplifier with two inputs. The noninverting terminal is connected to the internally
generated reference voltage. The inverting
terminal is connected to full regulated output
voltage. The series pass transistor is driven by
the error amplifier. This transistor acts as a
variable resistor and regulates the output
voltage. The circuitry to limit the current is used
to stop the flow of excess current passing
through the circuit. The frequency compensation
terminal is used to decide the frequency
response of the error amplifier. The simplified
internal structure of IC 723 is shown in fig 2:
The maximum ratings of IC 723 is shown in fig 3:
fig 2
Sr No
Parameter
Maximum value
1
Pulsed Voltage
50 V
2
Continuous Voltage
40 V
3
40 V
6
Input Output Voltage
Differential
Maximum Amplifier Input
Voltage-Either Input
Maximum Amplifier Input
Voltage-Differential
Internal Power Dissipation
660 mW
7
Output Current
150 mA
4
5
Reference : www.circuitstoday.com
fig 3
LAB:- CEII (SEM V EXTC)
8.5 V
5V
Design Problem
Question:-Design a voltage regulator IC 723 for following specifications: V0=5V
; I0=100mA; Vin= 15±20%; ISC= 150mA; Vsense=0.7V
• Solution: Rsc=
𝑉𝑠𝑒𝑛𝑠𝑒
=?
𝐼𝑠𝑐
Neglecting input bias current
R 1=
𝑉𝑟𝑒𝑓−𝑉𝑜
=?
𝐼𝑜
VO= Vf
𝑅2
+
𝑅1+𝑅2
R2=?
R3=R1//R2=?
LAB:- CEII (SEM V EXTC)
• Procedure:
1)Design the given problem and connect the circuit.
2)Apply unregulated input voltage at pin 12.
3)Check the output at pin 2 using the multimeter.
4)Note the output and vary the input voltage.
5)Repeat steps 2 to 4 till Vcc=25V.
• Observation:
Input Unregulated Voltage (V)
Regulated Output Voltage (V)
• Result :
The regulator output is constant at 5.07 over range of inputs of 15-25V using IC723.
LAB:- CEII (SEM V EXTC)
References
•
Internet and Books by Sergio Franco and Ramakant Gaykwad
LAB:- CEII (SEM V EXTC)