JPS5981906A - Frequency converting circuit - Google Patents

Abstract

PURPOSE:To reduce an operating voltage by decreasing the number of transistors (TR) connected in series. CONSTITUTION:A signal received by an antenna coil 7 is applied to the bases of TRs 14 and 17 in a frequency converting circuit 1. The oscillation output of a local oscillator 2 is applied to the base of a TR19 and also applied to the base of a TR18 through a phase inverting circuit 33. Therefore, antiphase oscillation outputs appear at the collectors of the TRs 18 and 19 and are applied to the emitters of TRs 14, 15, 16, and 17. Then, frequency-converted intermediate frequency signals are led out from the collectors of the TRs 15 and 17 through an intermediate frequency transformer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a frequency conversion circuit used in radio receiver stereo equipment and the like.

1. Configuration of Conventional Example and Its Problems FIG. 1 shows a typical -flI of a conventional frequency conversion circuit. In FIG. 1, the signal is received by the anti-coil 7, capacitor 6, no (the signal tuned by the recon 6 constitutes the frequency conversion circuit 1), the transistor 14.1
Added to the base of 7. On the other hand, the oscillation signal of the local oscillator circuit 2 is applied to the base of the transistor 220, and the oscillation signal is applied to the base of the transistor 190 from the emitter of the transistor 22. When the local oscillation [1 path 2 oscillation signal is applied to the base of the transistor 19, the l-transistor 1
Local oscillation signals having opposite phases are output to the collectors of transistors 14 and 14, respectively. ．． 15 and 16
．． Each of the 17 emitters is assigned a signal.

Then, the frequency-converted intermediate frequency signal is taken out by the intermediate frequency transformer 8 connected to the collectors of the transistors 115 and 17. Here transistor 12.20.23
is a transistor for current supply, and the bias circuit 3 supplies the base-to-base voltage of the transistor 12.20°23.The transistor 11 is also used to make the base of the transistor 18 almost the same potential as the base of the transistor 19. It has been established. If transistor 11
This is because, if .degree. 22 were not present, the base voltages of the transistors 12 and 19 would be the same as those of the transistors 14 to 17, and the transistors 14 to 17 would not operate together.

In the conventional frequency conversion circuit explained above, the transistor 1
4-17. Transistor 1B, 19.1-Transistor 2
Approximately 1.5 to 1 because each 0 is connected in three stages in series.
．． It only works at low voltages, up to 8V. (When the potential between the base and emitter of the transistor is about 0.7V) Also, the bias circuit 3 often uses two diodes 27.28, and the disadvantage is that the bias circuit only operates stably up to about 1.4V. There is.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks, and aims to provide an excellent frequency conversion circuit that can operate satisfactorily up to lower voltages than conventional frequency conversion circuits. be.

Structure of the Invention The present invention has two stages of series connection of transistors, and is configured to operate up to a low voltage.

DESCRIPTION OF EMBODIMENTS FIG. 2 is an electrical wiring diagram of an embodiment of the frequency conversion circuit of the present invention. In FIG. 2, the signals are received by the antenna coil 7, and the capacitor 5. The signal tuned by the variable capacitor 6 is applied to the bases of transistors 14 and 17 in the frequency conversion circuit 1. On the other hand, the oscillation output of the local oscillation circuit 2 is applied to the base of the transistor 19 and is also applied to the base of the transistor 18 through the phase inversion circuit 33.

Therefore, the oscillation outputs having opposite phases appear at the collectors of transistors 18 and 19, respectively, and are applied to the emitters of transistors 14 and 15 and 16 and 17, respectively. Therefore, a frequency-converted intermediate frequency signal appears from the collector of the transistor 15, 17, and is taken out via the intermediate frequency transformer 8. At this time, if there is no phase inversion circuit 33 and local oscillation signals of the same phase are applied to the transistors 18 and 19, the local oscillation signal tends to leak to the intermediate frequency transformer 8, which is inconvenient. By applying local oscillation signals of opposite phases to the bases of transistors 18 and 19 (7), the leakage of the local oscillation signals in the output example of transistors 15 and 17 cancel each other out, and the signals are taken out from the intermediate frequency transformer 8. This has the advantage that the leakage of the local oscillation signal caused by the leakage is significantly reduced.

The base bias of the transistor 18.1g is provided by the bias circuit 301 diodes and the voltage is transferred to the resistor 31.
．． 32, transistors 18 and 19 operate at approximately 0.7V. Also, when the 10B power supply decreases, the emitters of transistors 14 to 17 become 0 from the 10B power supply.
．． Transistors 18, 19, 14 to 17 operate until the TV voltage becomes low and the voltage between the emitter and collector of transistor 18, 19 becomes 0.1 to 0.2V. For this reason,
According to the above embodiment, sufficient operation can be achieved even at a low voltage of 0.8 to 0.9 V-i.

FIG. 3 shows another embodiment of the bias circuit 3. According to this bias circuit 3, stable operation can be performed even at lower voltages. By using this bias circuit 3, it is possible to operate the transistors 18 and 19 at a voltage as low as 0.8 to 0.9V with a small change in current. In FIG. 3, a transistor 44 has its base and collector connected to each other, and may be a diode.

The resistor 43 is a starting resistor and has a high resistance. When 10B magnetic pressure is applied, a current flows through the starting resistor a3 and the diode connection (
Current flows through the transistor 42 whose collector and base are connected. The transistors 42 and 41 constitute a current mirror circuit, and when a current flows through the transistor 42, a current also flows through the transistor 44.Therefore, current also flows through the transistors 45 and 46, and the entire circuit becomes operational. Now, suppose that when a current of 200 μA flows through the transistor 44, its vBE (potential between base and emitter) is approximately 0.7 V. (Figure 4a) Transistors 41 and 42 constitute a current mirror circuit. Since almost the same current flows through the transistor 42
A current of 2oO/iA flows through the transistor 46.46
1/2 of that, 1ooμA, flows through each of them. As already shown in FIG.
When BE becomes approximately 0.65V, a current of 200 μA, which is the sum of the currents of transistors 45 and 46, flows through the resistor 47, and the voltage drop is 0.06V. Therefore, the resistance 47 becomes 2509, and the transistor 44 has a resistance of 20.
0μA flows and it operates stably.

This bias circuit operates even if the voltage between the emitters and collectors of the transistors 41, 45, 46 is as low as 0.1 to 0.2V, and the diode-connected transistors 42, 44
Since the base-emitter voltage of the transistor 44 is approximately 0.7V, it will operate even if the voltage becomes as low as 0.8 to 0.9V, and because of the feedback loop circuit, the transistor 44 can operate up to this low voltage. almost the same current flows. From point A, transistor 1 constituting the frequency conversion circuit in FIG.
In addition to the base of 8.19, transistors 18 and 19 of the frequency conversion circuit and this transistor 44 operate as a current mirror circuit and can stably supply current down to a low voltage. Further, although the intermediate frequency transformer 8 is connected to the collectors of the transistors 15 and 17 to take out the signal, the signal may be taken out from the collectors of the transistors 14 and 16.

FIG. 5 is an electrical wiring diagram of still another embodiment of the frequency conversion circuit of the present invention. In Figure 5, local oscillation circuit 2
1 phase inversion circuit 33. The bias circuit 3 is shown more specifically. The local oscillation circuit 2 oscillates with transistors 54 and 55, and oscillates with oscillation coils 53. Capacitor 52. Fill the variable capacitor 51 and turn it on. The oscillation signal is transmitted by transistor 5
A current mirror circuit is formed between a diode (or diode-connected transistor) 57 on the collector side of 5 and a transistor 67, and the transistor 65.
It is added to the base of one transistor 66 of the differential circuit No. 6. Therefore, signals having mutually opposite phases are taken out to the collectors of transistors 65 and 65, and are applied to the bases of transistors 18 and 19. At this time, if the voltage drop across the resistors 64 and 67 is set to 0.1 to 0.2 V, the phase inversion circuit also operates up to a low voltage. transistor 6
The base bias of 1 and 62 uses the voltage of the diode-connected transistor 42 in the bias circuit 3, and the current of the transistor 63 is approximately 1 of the current of the transistor 56.
/2, so transistor 61 is
2 times the current flowing through transistor 63 (the currents of transistors 44 and 42 are almost the same).
When the resistors 64 and 67 are used in parallel, the same current flows through the resistors 64 and 67. When one transistor 63 is used, the resistor 64 is replaced by the resistor 6.
By setting the resistors 64 and 67 to half the value, the voltages of the resistors 64 and 67 can be made almost the same.

In the embodiment shown in FIG. 5, the starting resistor 43 is connected in series with a diode-connected transistor 44, but operates in the same manner as shown in FIG.

As described in detail, the present invention can provide a frequency conversion circuit that operates satisfactorily even at low power supply voltages, and is extremely advantageous in practice.

[Brief explanation of drawings]

FIG. 1 is an electrical connection diagram of a conventional frequency conversion circuit, FIG. 2 is an electrical connection diagram of one embodiment of the frequency conversion circuit of the present invention, and FIG. 3 is an electrical connection diagram of another embodiment of the same main part. Connection diagram, Figure 4 explains the same example/hime voltage and current characteristic diagram,
FIG. 5 is an electrical wiring diagram of still another embodiment. 1... Frequency conversion circuit, 2... Local oscillation circuit, 3... Bias circuit, 7...
Antenna coil, 5... Capacitor, 6...
...Varicon, 8...Intermediate frequency transformer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 4 Mungeshi (A)

Claims (1)

[Claims] 1st. The emitters of the second transistors are coupled together and connected to the collectors of the third transistor; The emitters of the fifth transistor are coupled together and connected to the collector of the sixth transistor, an antezo input signal is applied to the bases of the first and fifth transistors, and the first . Second. Third
．． The base potential of the fourth transistor is configured such that one voltage is applied to the base potential of the third transistor. The sixth base is biased by the contact potential between the base and emitter of one transistor or the voltage of one diode, and local oscillation signals of mutually opposite phases are applied to the bases of the third and sixth transistors. A frequency conversion circuit characterized in that it is configured to extract an intermediate frequency signal from the collectors of the fifth or second and fourth transistors.