JPS622815Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a power supply circuit, and an object of the present invention is to provide a power supply circuit that can reduce power consumption by supplying the power supply voltage of a plurality of transistors connected in series in series. purpose.

FIG. 1 shows a block system diagram of an example of a device having a high frequency signal switching device to which the present invention can be applied, and FIG. 2 shows a specific circuit diagram of an example of an amplifier including a conventional power supply circuit. Identical parts are given the same reference numerals. In FIG. 1, a television signal received by a receiving antenna 1 is supplied to a high frequency signal switching device 2. As shown in FIG. The high frequency signal switching device 2 shares the receiving antenna 1 with an existing television receiver 10 and a magnetic recording/reproducing device (VTR) 7, and
When recording a reverse program, the television broadcast signal is distributed to the VTR's built-in receiving section (tuner, IF stage) 8 and the television receiver 10, and the VTR 7
When monitoring and reproducing the reproduced signal, the RF converter 9 built in the VTR converts the reproduced television signal into an empty channel of television broadcasting, and supplies the reproduced television signal to the antenna terminal of the television receiver 10.

That is, the received television signal is transmitted through the amplifier 3 for loss correction by the distributor 4.
is supplied to the VTR7, where it is distributed into two parts, and one is supplied to the VTR7.
The other one is synthesized via an amplifier 5 provided for high frequency amplification for the mixing loss by a combining circuit 6 and isolation measures for the signal returned from the output stage to the input stage of the high frequency signal switching device 2. It is supplied to circuit 6. The synthesis circuit 6 mixes and synthesizes the received television signal from the amplifier 5 and the VTR reproduced television signal which has been RF converted into an empty channel from the RF converter 9, and simultaneously sends the synthesized television signal to the television receiver 10. Supplied to the antenna terminal.

As a result, during VTR playback, it is possible to monitor playback using an empty channel on the television receiver 10 without having to operate a switch.

As shown in FIG. 2, the above amplifier 5 has a received television signal input terminal 11 and a power supply terminal 12.
It has a configuration in which two stages of NPN transistors Q ₁ and Q ₂ are connected in series.

However, conventionally, the power supply voltage of the transistors Q ₁ and Q ₂ constituting the amplifier 5 is such that the power supply voltage +B from the terminal ₁₂ is applied in parallel to the collectors of the transistors Q ₁ and Q _{2, respectively, via the coils L 1 and L 2 .} Therefore, if the transistors Q ₁ and Q ₂ were configured to have a collector current of 34 mA, for example, a current of 68 mA or more would have to flow at least at the terminal 12, resulting in a disadvantage of high power consumption.

The present invention eliminates the above-mentioned drawbacks, and its embodiments will be described in conjunction with FIGS. 2 to 5.

FIG. 3 shows a specific circuit diagram of an amplifier to which the first embodiment of the power supply circuit according to the present invention is applied. In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. In this embodiment, the first power supply terminal 12 is connected to the collector of the transistor _Q2 via the first coil _L2 , and the emitter of the transistor _Q2 and the second power supply terminal GND are connected to each other.
An emitter resistor and bypass capacitor between
C ₁ is connected in series, and the connection point between capacitor C ₁ and emitter resistor constitutes an AC removal filter to complete high frequency bypass.
It is connected to the collector of the transistor Q ₁ via the coil L ₃ and the capacitor C ₂ and the coil L ₁ which is the second coil, respectively. These constitute an amplifier 5'.

As a result, for example, from the first power supply terminal 12
If a power supply voltage of 12V is applied, the voltage at the above point can be 6V. In other words, transistors Q ₁ and Q ₂ each have a power supply voltage of 6V, which is half of the power supply voltage of 12V.
is applied as the power supply voltage. Therefore, the necessary collector current of 34 mA can be obtained for each of the transistors Q ₁ and Q ₂ , and only about 34 mA of current needs to be passed through the power supply terminal 12 , making it possible to reduce power consumption compared to the conventional case.

Next, a second embodiment of the circuit of the present invention will be described. FIG. 4 shows a specific circuit diagram of an amplifier to which the second embodiment of the circuit of the present invention is applied. In the figure, the same components as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 4, an amplifier 5'' is composed of transistors Q ₁ , Q ₂ and others connected in series in two stages. In this embodiment, the point is the transistor Q via the second coil L _{4 1.} This coil L ₄ is composed of a balun coil, which has a particularly low frequency band characteristic (shown by the solid line in Figure 5) compared to when an air-core coil is used. The band characteristics can be improved. In FIG. 5, the broken line indicates the band characteristics of the balun coil.

In addition, in this embodiment, the high frequency amplification gain of the _two stages Q ₁ and Q is low, 10 dB or less, so it is possible to eliminate the need for the π-type AC removal filter using the coil L ₃ and capacitors C ₁ and C ₂ of the first embodiment. This was done in view of the fact that a sufficient bypass effect can be obtained with only the capacitor C ₁ , and thus half the voltage of the power supply voltage of the power supply terminal 12 can be applied to the collector of the transistor Q ₁ as the power supply voltage. The number of parts can be reduced compared to the first embodiment.

In the case of this embodiment as well, the potential difference between the collector of the transistor Q ₂ and the point and the potential difference between the collector of the transistor Q ₁ and the second power supply terminal (GND in this case) are respectively set to the first power supply terminal 12. Since the power supply voltage can be reduced to approximately 1/2, power consumption can be reduced compared to conventional methods.

As described above, the power supply circuit according to the present invention has a first power supply terminal connected to the collector of the second transistor in the rear stage of the amplifier via the first coil, and a first power supply terminal connected to the collector of the second transistor in the rear stage of the amplifier. a second power supply terminal to which the emitter is connected via a resistor;
a bypass capacitor connected between the emitter resistance of the second transistor and the second power supply terminal;
A second transistor connects the connection point of the bypass capacitor and the emitter resistor to the collector of the first transistor.
Since the power supply voltage is 1/2 of the potential difference between the first and second power supply terminals,
can be applied to each transistor, and therefore, power consumption can be reduced compared to a conventional power supply circuit in which the first power supply terminal is connected to the collectors of the first and second transistors, respectively. Also,
The second coil applies the power supply voltage applied to the second transistor from the first power supply terminal to the first transistor without unnecessary drop, and
It blocks the output signal of the first transistor from reaching the emitter of the second transistor to prevent interference between the first and second transistors, and also functions as a load for the first transistor. The desired effect can be obtained by minimizing the number of points, and when a balun coil is used as the second coil, the band characteristics can be improved compared to when an air-core coil is used. It is something that you have.

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an example of a device having a high frequency signal switching device to which the present invention can be applied, Fig. 2 is a specific circuit diagram showing an example of an amplifier including a conventional power supply circuit, and Figs. FIG. 4 is a specific circuit diagram showing an amplifier including the first and second embodiments of the circuit of the present invention, and FIG. 5 is a characteristic diagram for explaining the operation of FIG. 4. 2...High frequency signal switching device, 3, 5, 5',
5''...Amplifier, 7...Magnetic recording and reproducing device (VTR), 11...Received television signal input terminal, 12...First power terminal, GND...Second power terminal, L ₁ to L ₄ ... Coil, Q ₁ , Q ₂ ... NPN transistor for amplification, C ₁ ... Bypass capacitor.

Claims (1)

[Scope of utility model registration request] a first transistor that is supplied with an incoming signal to its base, amplifies it, and outputs it from its collector;
In a circuit for supplying a power supply voltage to an amplifier comprising a second transistor which receives a signal from the collector of the transistor at its base, amplifies the signal, and outputs it from the collector, a first power supply terminal connected via a coil, a second power supply terminal connected to an emitter of the first transistor in the front stage of the amplifier via a resistor, and an emitter of the second transistor. A power supply comprising a bypass capacitor connected between a resistor and the second power supply terminal, and a second coil connecting a connection point between the bypass capacitor and the emitter resistor and the collector of the first transistor. circuit.