JPH01162021A - Am/fm receiving circuit - Google Patents

Abstract

PURPOSE:To improve the terminal utilizing efficiency of an integrated circuit by causing a terminal for AM and FM mode switching control and a terminal for FM detecting coil connection to be common and obtaining two function in an integrated circuit AM/FM receiver. CONSTITUTION:The terminal for FM detecting coil 3 connection and the terminal of an AM and FM operation switching control circuit 8 are shared by one terminal (c). In an FM demodulating block 9, a quad latch detecting circuit is constituted. When a switch 7 is turned on, a power source voltage VCC is impressed through the detecting coil 3 to the switching control circuit 8 as a control voltage and as a result, the switching circuit 8 is operated so that an AM tuner block 6 can go to an operation stopping condition and the FM demodulating circuit block 9 can go to an operating condition. Since the force resistance of the switching circuit 8 is caused to be enough high, an influence is hardly given to the phase shifting characteristic of the detecting coil 3. When the switch 7 is turned off, the switching circuit 8 executes a switching so that the AM tuner block 6 can go to the operating condition and the FM demodulating circuit block 9 can go to the operation stopping condition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radio receiver, and in particular to an integrated circuit A
The present invention relates to the configuration of an AM/FM operation switching circuit in an M/FM receiving circuit.

[Conventional technology]

Traditionally, AM/FM of integrated circuit AM/FM receivers
For mode switching, a dedicated switching control terminal connected to the switching control circuit is provided, and the switching control circuit controls the operation of the AM circuit block and the FM circuit block according to the voltage applied to the switching control terminal. I was going there.

[Problem that the invention seeks to solve]

The above-mentioned conventional AM/FM receiver has a dedicated FM/AM mode switching control terminal, so it has the disadvantage that the terminal usage efficiency is low in semiconductor integrated circuits that are packaged in a package with a predetermined number of terminals. .

[Means for solving problems]

In the AM/FM receiving circuit of the present invention, the FM detection coil acts as a phase shifter of the quadrature detection circuit and serves as a path for applying a control voltage to the switching control circuit.
In other words, one end of the detection coil is connected to the IC, and the other end of the detection coil is connected to the IC.
When connected to a predetermined bias source, the receiver operates in FM mode, and when disconnected, it operates in AM mode.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diaphragm of one embodiment of the present invention. a is the FM intermediate frequency signal input terminal, b is the AM high frequency signal input terminal, C is the FM detection coil connection terminal, d is the detection output terminal, and 1 is the FMIF! J-mitting amplifier, 2 is buffer amplifier, 4 is capacitor, 3 is FM detection coil, 5
is a multiplier, 6 is an AM tuner block, 7 is a switch, 8 is a switching control circuit, 9 is an FM demodulation circuit block, and F
The M demodulation block 9 is configured with a conventional odd-ratch detection circuit. When the switch 7 is turned on here, the power supply voltage VCC is applied to the switching control circuit 8 as a control voltage via the detection coil 3, and as a result, the switching circuit 8 puts the AM tuner block 6 into a non-operating state and puts the FM demodulation circuit into a non-operating state. Block 9 operates to be operational.

Furthermore, by setting the input resistance of the switching circuit 8 to a sufficiently high value, the phase shift characteristics of the detection coil 3 can be hardly affected. Next, when the switch 7 is turned OFF', the switching circuit 8 switches the AM tuner block 6 to the operating state and the FM demodulation circuit block 9 to the non-operating state.

〔Effect of the invention〕

As explained above, in an integrated circuit AM/FM receiver, the present invention utilizes the terminals of the integrated circuit by making the terminal for controlling the AM-FM mode and the terminal for connecting the FM detection coil common to provide two functions. This has the effect of improving efficiency and allowing surplus terminals to be used for necessary terminal functions when incorporating other new functions into the integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diaphragm showing one embodiment of the present invention. a...FM intermediate frequency signal input terminal, b...
...AM high frequency input signal terminal, C...FM detection coil connection terminal, d...detection output terminal, 1...
...FM! J Mitting, 2... Buffer amplifier, 3... Detection coil, 4... Coupling capacitor, 2... Multiplier, 6...
... AM tuner block, 7 ... switch, 8 ... switching control circuit, 9 ... FM
Demodulation circuit block. Agent Patent Attorney Uchihara Oto8~ ＼

Claims (1)

[Claims] The terminal for connecting the FM detection coil and the terminal for switching AM/FM operation are shared by one terminal, and when the other end of the FM detection coil is connected to a predetermined bias power supply, the FM
AM/FM receiving circuit operated in AM mode and in AM mode when left open.