LA7775M Ver la hoja de datos (PDF) - SANYO -> Panasonic
Número de pieza
componentes Descripción
Fabricante
LA7775M Datasheet PDF : 5 Pages
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LA7775M
Design Notes
1. RF amplifier
This circuit is formed as a two-transistor cascode amplifier and takes an LC tank
circuit as its load. The operating current is set by the external resistor connected to
pin 22. The optimal operating current is between 1.5 and 2 mA. The capacitor
(C2) connected between pins 23 and 24 is related to the tank circuit Q, and must
not be too large.
C1
C2
23 24
21 22
2. Oscillator circuit
T00090
This is a grounded collector oscillator circuit, and supports using either an LC, a crystal, or a SAW resonator. Care is
required when constructing this circuit, since the input sensitivity may be suppressed if the oscillator circuit output
leaks into the IF limiting amplifier. It is extremely important to use a capacitor (e.g. a ceramic capacitor) with
excellent high-frequency characteristics for the 1000 pF bypass capacitor inserted between the oscillator circuit power
supply pin (pin 6) and the ground pin (pin 1). In addition, this capacitor must be located as close as possible to pins 1
and 6. When forming an oscillator circuit using a SAW resonator, the optimal values for C1 through C3 will vary
with the oscillator frequency. Thus this circuit must be adjusted for optimal
performance. Since the capacitor C3 between pin 3 and ground will be shared if a
circuit that switches between two SAW resonators is used, the difference between
34
5
C1
C2
the frequencies must be held to under 10 MHz. If a large frequency difference is
C3
required, design a circuit that also switches the capacitance between pin 3 and
ground.
T00091
3. IF limiting amplifier
This circuit consists of a six-stage direct coupled differential amplifier to which DC feedback is applied. Since an
internal 1-kΩ resistor is built in between the IF input pin (pin 9) and pin 11, the input and output impedance of the
330-Ω IF filter can be matched with an external 510-Ω resistor. No external matching resistor is required for the IF
output (pin 7), since a 330-Ω resistor is built in.
4. Quadrature detection circuit
An external phase shifting circuit is formed from an LC tuning circuit and a ceramic discriminator.
12
13
12
13
390 W
4 kW
T00092
T00093
s No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace
equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of
which may directly or indirectly cause injury, death or property loss.
s Anyone purchasing any products described or contained herein for an above-mentioned use shall:
Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and
distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all
damages, cost and expenses associated with such use:
Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on
SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees
jointly or severally.
s Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for
volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied
regarding its use or any infringements of intellectual property rights or other rights of third parties.
This catalog provides information as of June, 1997. Specifications and information herein are subject to change
without notice.
No. 5736-5/5
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