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MC1596G Datasheet PDF : 12 Pages
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OPERATIONS INFORMATION (continued)
—
The linear signal handling capabilities of a differential amplifier
are well defined. With no emitter degeneration, the maximum
input voltage for linear operation is approximately 25 mV peak.
Since the upper differential amplifier has its emitters internally
connected, this voltage applies to the carrier input port for all
conditions.
Since the lower differential amplifier has provisions for an
external emitter resistance, its linear signal handling range mav be
adjusted by the user. The maximum input voltage for linear op-
eration mav be approximated from the following expression:
()( V = 15 RE)volts peak.
This expression may be used to compute the minimum value of
RE for a given input voltage amplitude.
The gain from the modulating signal input port to the output is
the MC1596/MC1496gain
parameter which is most often of interest
to the designer. This gain has significance onlv when the lower
differential amplifier is operated in a linear rode, but this includes
most applications of the device.
As previously mentioned, the upper quad differentiali~,rn~$$fier
may be operated either in a linear or a saturated mod%, %Q,~*Ski-
mate gain expressions have been developed for \#e ,h~i~$596/
MC1496 for a low-level
carrier input conditions:
1) Low-level dc
2) High-level dc
3) Low-level ac
4) High-level ac
modulating
signal input an~i~~:$t,$’llowing
~,~$*.{:“y:>>3,!,‘:‘.*$\)}?),.>\.$’ ,
“t:,~.~;”,.,,t.<?,:~!?>?%. $~(-~”’
,:, .t,t,“.’..?../>,?:...;y>,’.~,}‘’%,i$*,‘,~>.~:i.,;-~>:>:*;\
VOLTAGE
FIGURE 25 – TABLE 1
GAIN AND OUTPUT FREQUENCIES
Carrier Input
Signal (Vc)
I
Approximate
Volmge Gain
I
Output Signal
Frequency
I
RLVC
Low-level dc
fM
2(RE + 2re) (~)
High-level dc
I
RL
RE +2re
I
fM
I
Vc is Ca@V~ Inp&t V~ltage.
“.’
2. When ~~$~sput
signal contains multiple frequencies,
the$~~~~~$%pression given is for the output amplitude of
$~h~..pf.~]he two desired outputs, fc I fM and fc – ‘M.
3. .*fi+$ g%n expressions are for a single-ended output. For
~,,$ ~~,ifferential output connection, mu Itiply each expres-
,..,~,.}.*,>:,:, sion by two.
High-level ac
0.637 R L
RE+2re
,:,, ~$,t,~{,,
~.,\,.&\
fc ~f M;,<-;+;*,
“
5fc +Q(6?..” ‘:;&.
,x..$“:.~,}?~,){... .!.
.:.:Q, ),.;....J?,e\:,‘>\y’,,.\‘.,:::
.~>.,, ‘;,,),$!
—
7. K = Boltzmann’s Constant, T = temperature in degrees
Kelvin, q = the charge on an electron.
KT
— s 26 mV at room temperature
q
Double sideband suppressed,td~~~~~{$i% ovulation is the basic
application of the MCI 596/%1 4%. The suggested circuit for
this application is shown ~n tfi~x>~ont page of this data sheet.
I n some application:~$~~+mav
be necessary to operate the
MC1596/MCl 496 with ~,”3$~~&dc supply voltage instead of dual
supplies. Figure 2G~$Q,@s’2 balanced modulator designed for
operation with a $.i)o!..~.. ,$‘,.~,?’~ Vdc supply. Performance
cuit is similar .<tao%+~\,.,,yh),.~~~,\:*.~aF, .khedual supply modulator.
of this cir-
AM Modula~r
f’<:+”
....}; .,,,,;,.,~,!,8
The.,$$fr&Ji,$”Yhown in Figure 27
mod~latq~~wlth a minor modification.
mav
be used as an amplitude
~~~+~q~ is required to shift from suppressed carrier to AM
opera~n is to adjust the carrier null potentiometer for the proper
amoun% of carrier insertion in the output signal.
However, the suppressed carrier null circuitrv as shown in
Figure 27 does not have sufficient adjustment range. Therefore,
the modulator may be modified for AM operation by changing
two resistor values in the null circuit as shown in Figure 28.
Product Detector
The MC1596/MC1496
tor (see Figure 29).
makes an excellent SSB product detec-
This product detector has a sensitivity of 3.0 microvolt and a
dynamic range of 90 dB when operating at an intermediate fre-
quencv of 9 MHz.
The detector is broadband for the entire high frequency range.
For operation at very low intermediate frequencies down to 50
kHz the 0.1 #F capacitors on pins 7 and 8 should be increased to
1.0 #F. Also, the output filter at pin 9 can be tailored to a
specific intermediate frequencv and audio amplifier input im-
pedance.
As in all applications of the MC1596/MC1496,
the emitter
resistance between pins 2 and 3 may be increased or decreased to
adjust circuit gain, sensitivity, and dynamic range.
This circuit may also be used as an AM detector bv introducing
carrier signal at the carrier input and an AM signal at the SSB
input.
The carrier signal mav be derived from the intermediate fre-
quency signal or generated locally. The carrier signal may be in-
troduced with or without modulation, provided its level is
sufficiently high to saturate the upper quad differential amplifier.
If the carrier signal is modulated, a 300 mV(rms) input level is
recommended.
MOTOROLA
@
Semiconductor Products Inc.
8
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