HIMACHAL PRADESH UNIVERSITY

DEPARTMENT of PHYSICS

PRoJECT REPoRT
oN
IC-723 VoLTAgE AND CURRENT
REgULATIoN

SESSIoN – 2024-2025
SUbMITTED bY
M.SC. 1 SEMESTER
ST

RAHUL bHATIA 3505

SIDDHARTH SHARMA 3506
SUDESH THAkUR 3507
ANSHUL 3508
 INTRoDUCTIoN
This report is about IC 723 Voltage and
Current regulation submitted by the
M.Sc. Physics 1st semester. In this report
we try our best to give you the
introduction of what really voltage
regulator is & how it works. We hope
that this report will acts as a manual for
all those students who really want to
learn and want to practically perform
the voltage and current regulation
experiment. We wish you all the best for
the comping experience…
AIM: - To study the performance of
IC 723 voltage regulator in the following
circuit configuration:
a) As a Voltage regulator (7V -12 V)
b) As a current regulator (20 mA)

APPARATUS: - Integrating Circuit

regulator type 723, connecting wires,
connecting wires, external power source.

bLoCk DIAgRAM: -
bASIC-CIRCUITS:-
WoRkINg of IC723 VoLTAgE REgULAToR
The internal working can be explained by dividing it
into two blocks, the reference voltage
generator and the error amplifier. In the reference
voltage generator, a Zener diode is being compelled to
operate at fixed point (so that Zener output voltage is a
fixed voltage) by a constant current Source which
comes along with an amplifier to generate a constant
voltage of 7.15V at the Vref pin of the IC.
As for the error amplifier section, it consists of an error
amplifier, a series pass transistor Q1 and a current
limiting transistor. The error amplifier can be used to
compare the output voltage applied at Inverting input
terminal through a feedback to the reference voltage
Vref applied at the Non-Inverting input terminal. These
connections are not provided internally and so has to
be externally provided in accordance with the required
output voltage.
The conduction of the transistor Q1 is controlled by the
error signal. It is this transistor that controls the output
voltage
PIN oUT 723 VoLTAgE REgULAToR
V+ and V-
These are the supply voltage terminals of the IC. V+ is the positive terminal and
V- is the negative terminal. The voltage difference between these terminals
should be between 9.5V to 40V.

Non-Inverting Input
This is the non inverting input of the error amplifier whose output is connected
to the series pass transistor. We usually give reference voltage or a portion of it
to the non inverting input.
Inverting Input
This is the inverting input of the error amplifier whose output is connected to
the series pass transistor. We usually give output voltage or a portion of it to
the inverting input. This makes the output voltage constant.
Vref
It is the reference voltage output of the IC. It is the output of voltage reference
amplifier. Its output voltage is about 7.15V.
Vout
It is the output terminal of the IC. Usually output voltage ranges from 2 to 37V.
This pin can provide up to 150mA current.
Current Limit
It is the base input of the current limiter transistor. This pin is used for current
limiting or current fold back applications.
Current Sense
This is the emitter of current limiting transistor. This terminal is used with
current limiting and current fold-back applications.
Vc
This is the collector input of the series pass transistor. It is usually directly
connected to the positive supply voltage if an external transistor is not used.
Freq. Comp
Frequency Compensation : This pin is used to connect a capacitor which
bypasses high frequency noises. It is the output of error amplifier. The
capacitor is connected between this pin and inverting input of the error
amplifier. The prescribed value of this capacitor varies for different types of
regulators. Please refer the datasheet for that.
Vz
It is the anode of the Zener diode whose cathode connected to the output
terminal. It is usually used for making negative regulators.

THEoRY :-
Voltage Regulator : a voltage regulator is a device which is used to provide an
output voltage which is essentially independent of load and line fluctuation .
Load regulation = No load output voltage – full load output voltage × 100 %
Full load output voltage
Here load regulation means the ability of power supply to maintain the
constant output voltage despite changes in output current and load. ideally the
load regulation should be zero meaning the supply’s output voltage is
independent of the load and remains the same throughout .
IC voltage regulator : It is an integrated circuit whose basic purposes is to
regulate the unregulated input voltage ( over a predefined range ) and provides
a constant regulated output voltage
For IC 723 load regulation specified as 0.01% for load current variation from
100 mA . A simple calculation will show that the drop in voltage from no load
to full load should be about 1mV only . In present unit the 20 V digital
voltmeter has a resolution of 10 mV and hence the drop in output voltage will
not be seen and the regulation will appear to be 0.1% .
If however the input voltage is too small for a particular output voltage setting ,
the output voltage with load may drop due to insufficient input voltage .
Note that the proper working - input voltage ≥ output voltage + voltage
needed in IC (min 5V)
The operation of voltage regulator is based on the principle of
feedback amplifier consider a negative feedback amplifier consisting
of operational amplifier of gain a potentiometer ratio of beta and
external load Rl and a reference source . A simple analysis shows that
for A ∞ the output is given by

𝑅1
𝑣 = (1 + )
𝑅2

The output voltage is therefore independent of the amplifier power

supply ( ±Vcc ) , amplifier gain (A) and the value of load resistor RL .
The output voltage may , however be varied by either varying Rrefrence
or the R1/ R2 . such a negative feedback amplifier while operating
within its linear region should serve as a voltage regulator provided
the operational amplifier is designed to carry the full load current
Integrated Circuit ( IC chip ) : an integrated circuit ( IC ), sometimes
called a chip or a microchip is a semiconductor wafer on which
thousands of tiny resistors , capacitors and transistors are fabricated .
An IC can function as an amplifier, oscillator, timer, counters,
computer memory or microprocessor. A particular IC is categorized as
either analog or digital , depending on its intended application

IC-723 : The 723 is a monolithic precision voltage regulator

constructed on single silicon chip . The device consist of temperature
compensated reference, error amplifier, series pass transistor and
current limit circuitry.
It mainly consist of following parts
1) REfERENCE gENERATINg bLoCk - The temperature
compensated Zener diode, constant current source & voltage
 reference amplifier together from the reference generating
block. The Zener diode is used to generate a fixed reference
voltage internally. Constant current source will make the Zener
diode to operate at affixed point & it is applied to the Non –
inverting terminal of error amplifier. The Unregulated input
voltage ±Vcc is applied to the voltage reference amplifier as well
as error amplifier.

2) ERRoR AMPLIfIER - Error amplifier is a high gain

differential amplifier with 2 input (inverting & Noninverting).
The Non-inverting terminal is connected to the internally
generated reference voltage. The Inverting terminal is
connected to the full regulated output voltage

3) SERIES PASS TRANSISToRS - Q1 is the internal series

pass transistor which is driven by the error amplifier. This
transistor actually acts as a variable resistor & regulates the
output voltage. The collector of transistor Q1 is connected to
the Un-regulated power supply. The maximum collector voltage
of Q1 is limited to 36Volts. The maximum current which can be
supplied by Q1 is 150mA.

4) CIRCUITRY To LIMIT THE CURRENT - The internal

transistor Q2 is used for current sensing & limiting. Q2 is
normally OFF transistor. It turns ON when the IL exceeds a
predetermined limit.Low voltage, Low current is capable of
supplying load voltage which is equal to or between 2 to
7Volts.Pin diagram of IC723 in figure 5.6.2. Vload = 2 to 7V and
Iload= 50mA
PRoCEDURE
foR VoLTAgE REgULATIoN
a) The circuit diagram of IC 723 as a voltage regulator is shown in
figure .
b) Make the connection as shown below
PIN 2 R2( resistor 2 ) 2nd end
R2(2nd end) 7 ( ground of IC or say lower potential)
R2(1st end) R1 ( 1st end )
R1 (2nd end) Emitter
R2 (1st end) Pin 4
Pin 5 Pin 6
Pin 7 Earth
Load Earth
c) After making the following connections note the reading of
voltage at various values of current . (at least 4 Readings)
d) Now change R1 and R2 accordingly and note the values.
e) Compare the values of calculated and observed value to
calculate output voltage using different values of R1 and R2 use
the formula

𝑅1
𝑣 = (1 + )Vref
𝑅2
 Example let r1 = 2k and r2 = 6.8k and Vref for IC is 7.15 then

2
𝑣 = (1 + ) 7.15 = 9.25
6.8

f) Do this for various values of resistance and compare the

observation and calculated values
g) Now Plot the graph between Current & voltage .

For current regulation -

a) Make the connection as shown below as
connect
Load (1.5) Pin4
Load (4.7) Load pin
R ( 6.8)2nd end 6 pin
Pin 7 earth
R (6.8 )1st end 5 pin
6 Pin Collector
Load 3.3 earth
b) Set the knob of the load for different load
and note the value of current by varying the
voltage .
c) Note the reading of current at different load
and plot the graph.
obSERVATIoNS AND TAbULATIoNS
VoLTAgE REgULATIoN
Sr no Current in mA Vout R1 R2 Vout (
(observed) calculated
1. a) 7.50 10.26
b) 8.50 10.26
c) 9.50 10.26 2 4.7 10.19
d) 10.50 10.26

2.
a) 7.10 9.32
b) 8.40 9.32 2 6.6 9.31
c) 9.30 9.32
d) 10.70 9.32
3. a) 9.70 12.21
b) 10.40 12.21
c) 11.30 12.21 4.7 6.8 12.09
d) 12.30 12.21

4. a) 11.20 13.02
b) 12.30 13.02
c) 13.20 13.02 6.8 8.2 13.16
d) 13.60 13.02

CURREN REgULATIoN:-
Sr no Current in mA Rload in kΩ

1 4.99 2

2 4.99 4.7

3 4.99 6.8
Graph :

Y-Values
12
10.26 10.26 10.26 10.26
10

8
Voltage in v

0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Current in mA

PRECAUTIoN:
1) Check your circuit very carefully before switching ON the
main switch
2) Check the IC and SL100 Transistors for heating . This may
happen due to wrong connection.
3) While taking observation in voltage regulator configuration
, more than 50 mA of current should not be drawn over an
extended period. This may damage SL 100 transistor
CoNCLUSIoNS :- After Performing above experiment we
conclude that
 IN VoLTAgE REgULATIoN :- As we vary the source input
current output voltage remains regulated or independent
load or line fluctuation.
IN CURRENT REgULATIoNS :- As we vary the source
voltage ,the output current regulated or remains constant .