The document discusses the application of phase-locked loops (PLL) in frequency shift keying (FSK) and frequency modulation (FM) demodulation, detailing the components and design considerations for voltage regulator ICs like LM317 and LM337. It highlights the advantages of using IC regulators, including ease of design, cost-effectiveness, and versatility, while providing information on fixed and adjustable output voltage options. Additionally, it explains the functioning of PLL in demodulating FM signals and the operation of discrete component regulators compared to IC regulators.

1. FSK , FM DEMODULATOR & VOLTAGE
REGULATOR ICS

2.  Application of PLL in FSK & FM demodulation three
terminal regulator ics.
 Adjustable output voltage regulator LM 317, LM 337
& LM 340 series power supply ics.
 Basic design considerations for designed regulated
power supply

4.  A divide by N network (frequency divider) is
connected externally between the VCO output and
phase comparator input.
 Since the output of the divider network is locked to
the input frequency fs, the VCO actually operates at a
frequency which is N times higher than fs.
fs = N fs
 The multiplying factor can be obtained by proper
selection of the scaling factor N of the frequency
divider.

6.  The FM signal which is to be demodulated is
applied at the input of the PLL.
 As the PLL is locked to the FM signal, the VCO
starts tracking the instantaneous frequency in the
FM input signal.
 The error voltage produced at the output of the
amplifier is proportional to the deviation of input
frequency from the center frequency FM.
 Thus the ac component of the error voltage
represents the modulating signal.
 Thus at the error amplifier output we get
demodulated FM output.

8.  FSK is used in computer peripherals and radio
communication of binary data or codes.
 The carrier frequency is shifted to either fH or fL
depending on whether a binary “1” or “0” is to be
transmitted respectively.
 Thus if a “1” is to be sent, the transmitter will
transmit a signal at frequency “fH” and if a “0” is to
this FSK signal can be demodulated by using PLL
as shown in fig.

10.  The discrete component regulator circuit such as the
zener voltage regulators are not much used in practice.
 Now a days the voltage regulator circuits are available
in the IC from and the IC regulators are widely used.
 Advantages of IC regulators:
1. The power supply design becomes easy & quick.
2. Cheap & easily available.
3. small hence they reduce the size of the power supply.
4. They are easy to use.
5. IC regulators are versatile.

11.  78XX series are three
terminal ,positive fixed
voltage regulators. Here XX
indicate the output.
 These regulators are
available in seven different
output voltage option, such as
5,6,8,12,15,18 and 24.
 Thus if we select a regulator
IC numbered “7812”, it
provides us a 12 V regulated
output voltage.

13.  Even though the 78XX series is fixed voltage
regulator series it is possible to obtain a variable
output voltage using it.
 The arrangement for obtaining a variable output
voltage is as shown in fig.
 The output voltage is varied by varying the variable
resister R2.
 Expression for output voltage :

15.  The block diagram shows that LM 317 is a series
regulator and a Darlington pair acts as a series pass
element.
 The output voltage is compared with the internally
generated voltage reference to produce an error
voltage which drives the Darlington transistors to
regulate the output voltage.
 RLIMIT is an internal sensing resistance. The voltage
across it is proportional to load current.
 This voltage is applied to the internal protection
circuitry. If the load current exceeds beyond its
maximum value, the Darlington pair will be
automatically turned off to protect the IC.
 Its o/p is adjustable over a range of 1.2 V to 37 V.

17.  The block diagram shows that LM 337 is a series
regulator and a Darlington pair acts as a series
pass element.
 The output voltage is compared with the internally
generated voltage reference to produce an error
voltage which drives the Darlington transistors to
regulate the output voltage.
 RLIMIT is an internal sensing resistance. The voltage
across it is proportional to load current.
 This voltage is applied to the internal protection
circuitry. If the load current exceeds beyond its
maximum value, the Darlington pair will be
automatically turned off to protect the IC.
 Its o/p is adjustable over a range of -1.25 V to -37 V.

18. LM 340XX

19.  These regular Ics are available in plastic power
package as shown in fig.
 It is three pin regulator with input, ground and
output terminals.
 The sequence of input, ground and output pins is
same as that of the 78xx IC.

20.  E draw max
 (for drawing)
 Analog Electronics
 (J. S. Katre)

21. Thank You……