FSK , FM DEMODULATOR & VOLTAGE REGULATOR ICS 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

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……