JPS61145936A - Radio reception circuit - Google Patents

Abstract

PURPOSE:To reduce its cost by connecting a constant current circuit of a frequency converting circuit and an AGC circuit in terms of DC to decrease the number of capacitors and terminals connecting them. CONSTITUTION:Emitters of the 1st transistor (Tr)1 and the 2nd Tr2 of a frequency converting circuit 31 are connected in common to a collector of the 5th Tr6 and emitters of the 3rd Tr4 and the 4th Tr5 are connected in common to a collector of the 6th Tr7. Further, bases of the 1st and 2nd Trs 1, 2 are connected, to which a local oscillating signal is fed, an intermediate frequency signal is extracted from at least one of collectors of the 1st and 3rd Trs 1, 4 or the 2nd and 4th Trs 2, 5, the emitters of the 5th and 6th Trs 6, 7 are connected to common via a common resistor 8, the bases of the 5th and 6th Trs 6, 7 are connected in terms of DC, an AGC signal is fed to a base of the 6th Tr7 and the base of the 6th Tr7 is connected to a constant current source and a bypass capacitor 37 is connected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a receiving circuit suitable for an AM radio broadcast receiver.

Conventional technology In recent years, the desire to make radio receivers smaller and lighter has led to the use of integrated circuits in their receiving circuits, but efforts to reduce external parts and the number of terminals are essential issues. .

A conventional radio receiving circuit will be described below with reference to the drawings.

FIG. 2 is an electrical wiring diagram of a conventional radio receiving circuit, in which 129 is an AGO signal generation circuit, 130 is a frequency conversion circuit, and 131 is a local oscillation circuit.

132 is a constant current circuit.

To explain the operation during reception, the antenna coil 13
5 To/< IJ Con134. The signal tuned by capacitor 133 is applied to a frequency conversion circuit 130. On the other hand, the local oscillation circuit is connected to the coil 139. Varicon 1
4o, a tuning circuit consisting of a capacitor 141, and transistors 117 and 118 for local silkworm generation connected to the secondary winding of the coil 139;
7 base.

The emitter is amplified in the same phase as the emitter and collector of the transistor 118 to create a positive feedback loop and oscillate. The local oscillation signal obtained here is applied to the base of the transistor 109 of the frequency conversion circuit 130 via an emitter follower constituted by the transistor 114. Then, the transistors 108 and 109 operate as an emitter-coupled differential amplifier, and oscillation signals with opposite phases are output to the collectors of the transistors 108 and 109, and the frequency conversion transistors 104 and 105
and the emitters of transistors 106 and 107. The signal received by antenna coil 136 is applied to the bases of transistors 104 and 107.

Transistor 104, 10S and transistor 10S
, 107 are emitter-coupled, so the oscillation signal from the emitter and the received signal from the antenna 135 are mixed with each other, and the output is sent to the transistor 10S.
, intermediate frequency coil 1 connected to the collector of 107
The signal is extracted as an intermediate frequency signal to the secondary side 137 of 36.

The constant current circuit consists of a current mirror circuit constituted by a constant current source 128 and transistors 127, 124, and 123 connected to the constant current source 128, and supplies power to the local oscillation circuit and the frequency conversion circuit. Next, the MGC signal generation circuit outputs each MGC signal according to the input level, turns on the transistors 101 and 102, operates to reduce the current of the frequency conversion circuit, and adjusts the gain of the frequency conversion circuit. This makes it possible to obtain an intermediate frequency signal with stable amplitude even when the input voltage is low.

Problems to be Solved by the Invention However, in the above circuit configuration, a bypass capacitor 142 is connected to the base common line of the constant current transistors 110, 112° 116 of the frequency conversion circuit to lower the impedance of the current source and to It is necessary to remove noise, and a capacitor 142 is connected to the AGCj circuit as a low-pass filter. Therefore, in an integrated circuit device having a limited number of terminals, two terminals are required to connect the capacitor, which is not preferable.

In order to solve the above-mentioned problems, the present invention provides a radio receiving circuit which aims to reduce the number of external components and the number of terminals of an integrated circuit device.

Means for Solving the Problems In order to solve the above problems, the radio receiving circuit of the present invention connects the emitters of the first transistor and the second transistor of the frequency conversion circuit in common to the collector of the fifth transistor. At the same time, the emitters of the third transistor and the fourth transistor are commonly connected to the collector of the sixth transistor, and the emitters of the first and fourth transistors are connected in common to the collector of the sixth transistor. The base of the second transistor is connected to apply a local oscillation signal, and the base of the first transistor is connected. a third transistor or a second transistor; An intermediate frequency signal is extracted from at least one of the collectors of the fourth transistor.

Above 5. The emitter of the sixth transistor is grounded through a common large resistor. A configuration in which the base of the sixth transistor is connected in a DC manner, a MU0C signal is applied to the base of the sixth transistor, and the base of the sixth transistor is connected to a constant current source and a bypass capacitor is connected. It is equipped with the following.

Operation The present invention has the above-mentioned configuration, and provides a capacitor that has the function of a low-pass filter that is similar to the conventional GO circuit, and a capacitor that bypasses the function of the capacitor for lowering the impedance of the constant current source of the frequency conversion circuit and reducing noise. It is possible to satisfy the following.

Embodiment A radio receiving circuit according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a part of a radio receiving circuit in a first embodiment of the present invention. In FIG. 1, 31 is a frequency conversion circuit, and 32 is a local oscillation circuit.

33 is a constant current circuit.

To explain the operation during reception, antenna coil 3
5 and variable capacitor 36. The signal tuned by capacitor 34 is applied to frequency conversion circuit 31. The local oscillation circuit is a coil 40. It consists of a tuned circuit consisting of a 42° variable capacitor 43 and a local oscillation transistor 14.15 connected to the secondary winding of the coil 40, and is in phase with the base and emitter of the transistor 140 and the emitter and collector of the transistor 16. It is configured to be amplified to create a positive feedback loop and oscillate. The local oscillation signal obtained here is applied to the bases of transistor 1 and transistor 6 of frequency conversion circuit 31 via resistor 13. The signal received by antenna coil 35 is applied to the base of transistor 6. Then, the transistors 6 and 7 operate as an emitter-coupled differential amplifier, and reception signals having opposite phases are output to the collector of the transistor 6.7, and the emitter of the frequency conversion transistor 1.2 and the transistor 4.6 are connected to each other. Added to emitter.

Here, since transistors 1 and 2 and transistors 4 and 5 are emitter-coupled, the received signal from the emitter and the oscillation signal from the local oscillation circuit are mixed with each other, and the output is sent to the collectors of transistors 2 and 6. The signal is output as an intermediate frequency signal to the secondary side 39 of an intermediate frequency coil 38 connected to the intermediate frequency coil 38. The constant current circuit 33 includes a constant current source 29 and a transistor 1B connected thereto, 19°20.21
The collector of the transistor 18 is grounded via a diode 22 and a resistor 23, and is also connected to the base of a constant current source transistor 160 of the local oscillation circuit to determine the current of the local oscillation circuit. The collector of the transistor 19 is grounded via the diode 26 and the resistor 24, and the transistor 1 determines the base potential of the transistors 1 and 50 of the frequency conversion circuit.
The base of transistor 9 is connected to the base of transistor 9, which determines the base potential of transistors 2 and 4. The collector of the transistor 20 is grounded via a diode 28 and a resistor 27, and is also connected to the base of a transistor 7 of the frequency conversion circuit via a resistor 26 and the base of a transistor 6 via a secondary winding of an antenna coil 35. The current of the frequency conversion circuit is determined. The MuGC signal generation circuit 30 connects this output to a MuGC control transistor 4 whose emitter is grounded.
The collector of this transistor 41 is connected to the base of the WkL transistor 6 via the transistor 7 of the frequency conversion circuit and the antenna coil 35. Here, a large input signal is input from the antenna coil 35, and the AGO signal output from the AGO signal generation circuit 30 is
The GO control transistor 41 is turned on.

It operates to lower the base potential of transistor 7 of the frequency conversion circuit and transistor 6 coupled in direct current.

With the above configuration, in this embodiment, the capacitor 37 connected to the base of the transistor 7 can fulfill the functions of the constant current source bypass capacitor and the MGO circuit low-pass filter capacitor shown in the conventional example. be able to.

Effects of the Invention As described above, the present invention connects the constant current circuit of one frequency conversion circuit and the mu GC circuit in a direct current manner, thereby reducing the bypass capacitor for the constant current source and the capacitor for the low pass filter of the five GO circuit. It is possible to satisfy two functions with one capacitor, reducing the number of capacitors and at the same time reducing the number of terminals for connecting capacitors, making it ideal for integrated circuit devices that require design with a limited number of terminals. A large cost reduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a tuner section of a radio receiving circuit according to an embodiment of the present invention, and FIG. 2 is a tuner circuit diagram of a conventional radio receiving circuit. 31... Frequency conversion circuit, 32... Local oscillation circuit, 33... Constant current circuit, 30...
...AGC signal generation circuit, 41...AGC transistor.

Claims (1)

[Claims] Frequency conversion circuit, local oscillation circuit, intermediate frequency amplification circuit, A
M detection circuit, the emitters of the first and second transistors of the frequency conversion circuit are connected in common to the collector of the sixth transistor, and the emitters of the third and fourth transistors are connected in common to the collector of the sixth transistor. A local oscillation signal is connected to the collector of the transistor, and a local oscillation signal is applied to the bases of the first and fourth transistors. A frequency signal is taken out, the emitters of the fifth and sixth transistors are grounded via a common resistor, an input signal is applied to the base of the fifth transistor, and the base of the sixth transistor and the fifth transistor are connected to each other. A radio receiving circuit characterized in that bases of the transistors are connected in a DC manner, an AGC signal is applied to the base of the sixth transistor, and a bypass capacitor is connected to the base of the sixth transistor.