Power supply is realized with mains transformer and Linear transistorized power supply stabilizer, A DC power supply apparatus includes a rectifier circuit which rectifies an input commercial AC voltage. The rectifier output voltage is smoothed in a smoothing capacitor. Voltage stabilization is provided in the stabilizing circuits by the use of Zener diode circuits to provide biasing to control the collector-emitter paths of respective transistors.A linear regulator circuit according to an embodiment of the present invention has an input node receiving an unregulated voltage and an output node providing a regulated voltage. The linear regulator circuit includes a voltage regulator, a bias circuit, and a current control device.
The bias circuit may include a bias device and a current source. The bias device has a first terminal coupled to the output terminal of the voltage regulator and a second terminal coupled to the control electrode of the current control device. The current source has an input coupled to the first current electrode of the current control device and an output coupled to the second terminal of the bias device. A capacitor may be coupled between the first and second terminals of the bias device.
In the bias device and current source embodiment, the bias device may be implemented as a Zener diode, one or more diodes coupled in series, at least one light emitting diode, or any other bias device which develops sufficient voltage while receiving current from the current source. The current source may be implemented with a PNP BJT having its collector electrode coupled to the second terminal of the bias device, at least one first resistor having a first end coupled to the emitter electrode of the PNP BJT and a second end, a Zener diode and a second resistor. The Zener diode has an anode coupled to the base electrode of the PNP BJT and a cathode coupled to the second end of the first resistor. The second resistor has a first end coupled to the anode of the Zener diode and a second end coupled to the reference terminal of the voltage regulator. A second Zener diode may be included having an anode coupled to the cathode of the first Zener diode and a cathode coupled to the first current electrode of the current control device.
A circuit is disclosed for improving operation of a linear regulator, having an input terminal, an output terminal, and a reference terminal. The circuit includes an input node, a transistor, a bias circuit, and first and second capacitors. The transistor has a first current electrode coupled to the input node, a second current electrode for coupling to the input terminal of the linear regulator, and a control electrode. The bias circuit has a first terminal for coupling to the output terminal of the linear regulator and a second terminal coupled to the control electrode of the transistor. The first capacitor is for coupling between the input and reference terminals of the linear regulator, and the second capacitor is for coupling between the output and reference terminals of the linear regulator. The bias circuit develops a voltage sufficient to drive the control terminal of the transistor and to operate the linear regulator. The bias circuit may be a battery, a bias device and a current source, a floating power supply, a charge pump, or any combination thereof. The transistor may be implemented as a BJT or FET or any other suitable current controlled device.
PHILIPS TDA2549 I.F. amplifier and demodulator for multistandard TV receivers:
The TDA2549 is a complete i.f. circuit with a.f.c., a.g.c., demodulation and video preamplification facilities for
multistandard television receivers. It is capable of handling positively and negatively modulated video signals in both
colour and black/white receivers.
• Gain-controlled wide-band amplifier providing complete i.f. gain
• Synchronous demodulator for positive and negative modulation
• Video preamplifier with noise protection for negative modulation
• Auxiliary video input and output (75 Ω)
• Video switch to select between auxiliary video input signal and demodulated video signal
• A.F.C. circuit with on/off switch and inverter switch
• A.G.C. circuit for positive modulation (mean level) and negative modulation (noise gate)
• A.G.C. output for controlling MOSFET tuners.
THOMSON TDA3190 COMPLETE TV SOUND CHANNEL:
The TDA3190 is a monolithicintegratedcircuit in a
16-lead dual in-line plastic package.It performsall
the functionsneededfor the TV soundchannel :
.IF LIMITER AMPLIFIER
.AF OUTPUT STAGE
The TDA3190 can give an output power of 4.2 W
(d = 10 %) into a 16 Ω load at VS = 24 V, or 1.5 W
(d = 10 %) into an 8 Ω load at VS = 12 V. This
performance,togetherwiththe FM-IF sectionchar-
acteristicsof high sensitivity, highAM rejection and
low distortion, enables the device to be used in
almost every type of televisionreceivers.
The device has no irradiation problems, hence no
externalscreening is needed.
The TDA3190 is a pin to pin replacement of
The electrical characteristics of the TDA3190 re-
mainalmost constantover the frequencyrange4.5
to 6 MHz, therefore it can be used in all television
standards (FM mod.). The TDA3190 has a high
or with a tuned circuit that provide the necessary
The value of the resistors connected to pin 9,
determinethe AC gain of the audio frequencyam-
plifier. This enablesthe desiredgainto be selected
in relation to the frequency deviation at which the
output stage of the AF amplifier, must enter into
CapacitorC8, connectedbetween pins10 and11,
determinesthe uppercutofffrequencyof the audio
C8 and C7 must be reduced, keeping the ratio
C7/C8 as shown in the table of fig. 16.
The capacitor connected between pin 16 and
ground, togetherwith the internal resistor of 10 KΩ
forms the de-emphasis network. The Boucherot
cell eliminates the high frequency oscillations
ULTRAVOX (SEMAR) P12 CHASSIS 2T/1 Preset tuner:
A preset tuner adapted for selecting a desired one out of a plurality of preset channels, comprising: a memory for storing digital data concerning a plurality of channels to be preset, push-buttons/rotatable knob for addressing the memory for reading the digital data of a desired channel, a digital/analog converter for converting the read digital data into an analog signal, a manually operable variable voltage generator to obtain search mode AFC assisted, a write-in/channel select mode selector, a switch circuit responsive to the mode selector switchable between the digital/analog converter and the variable voltage generator, a voltage controlled oscillator responsive to the output of the switch circuit, a tuner employing the voltage controlled oscillator as a local oscillator, a comparator for comparing the outputs of the digital/analog converter and the variable voltage generator, a counter to be reset responsive to the push-button search mode AFC and to be enabled responsive to the write-in mode output of the mode selector to make a counting operation as a function of the output of the comparator, the output of the counter being loaded as the digital data concerning a channel in the memory, as addressed, a reference oscillator, a frequency comparator for comparing the output of the reference oscillator and the intermediate frequency output of the tuner, a filter for filtering the frequency comparator output to provide a correction control signal to the digital/analog converter, the digital/analog converter being adapted to be corrected for deviation of the intermediate frequency of the tuner as a function of the correction control signal.
A typical conventional preset tuner such as employed in tv receivers and the like comprises a mechanical preset scheme. For example, such a preset tuner employing variable inductance devices as a tuning element is adapted to preset a plurality of channels by varying the inductance value of the variable inductance devices in association with the manual operation of a tuning knob. Another example of such a tuner using a variable capacitance device such as a variable capacitance diode as a tuning element employs variable resistors adjustable in association with the manual operation of a tuning knob for the purpose of a presetting operation.
Such preset tuners as described above as employing a variable inductance device, a variable capacitance device and the like require provision of the same number of variable inductance devices, variable resistors and the like as that of presetting channel selection switches, which makes the tuner large in size, with the result that such tuner is disadvantageous particularly in case where such tuner is employed in an indash type portable tv receiver, where the tuner is provided in a limited space.
Accordingly, a principal object of the present invention is to provide an improved preset tuner, wherein the data concerning the local oscillation frequencies corresponding to the respective preset channels is preloaded in a memory in a digital representation format.
Another object of the present invention is to provide an improved preset tuner, which is adapted for implementation by large scale integration integrated circuits.
A further object of the present invention is to provide an improved preset tuner, which is adapted for implementation in an electronic structure rather than mechanical structure