JPS59156005A - Amplifier circuit for high frequency detection output circuit - Google Patents

Abstract

PURPOSE:To attain circuit integration of all circuit elements without mounting externally a capacitor by designing the circuit so that a carrier signal is eliminated sufficiently by a small capacitance of a capacitor. CONSTITUTION:One electrode of a capacitor C' to eliminate a carrier signal is connected to a connecting point of both bases of the 1st and 2nd transistors (TR) T1, T2. The other electrode is connected to a power supply Vcc. In the constitution above, the 3rd TRT3 and the capacitor C' form a peak detecting circuit. When a signal charged in the capacitor C' is discharged, the 1st and 2nd TRs T1, T2 are included in the path of the discharge. Thus, even if a charging speed to this capacitor C' is increased by reducing the capacitance of the capacitor C' to a very small value, since the discharge speed is nearly a base current value of the 1st and 2nd TRs T1, T2, the discharge speed becomes very low. Then, since the peak detecting circuit is constituted by the 3rd TRT3 and the capacitor C', the carrier signal is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit used in an output stage of a high frequency IC.

Generally, the current output of FM quadrature detection or peak detection is inverted at the output stage by an amplifier circuit as shown in FIG. 1 in order to reduce the influence of power supply fluctuations. In FIG. 1, ■ is a current signal source, T1. T2
is a current reversal transistor, T3 is the transistor T
1. T2 is a base current correction transistor, OUT is an output terminal, k is a resistor, and C is a capacitor for dropping a carrier signal. By the way, this circuit can be implemented as an IC except for capacitor C, but capacitor C
For example, in the case of 21°4 in quadrature detection
A large capacitance is required to drop the MHz carrier signal, and for this reason it cannot be integrated into an IC and is instead attached externally.

The present invention provides an amplifier circuit for a high-frequency detection circuit that allows the entire circuit element to be integrated into an IC without externally attaching a capacitor by sufficiently dropping a carrier signal with a small-capacity capacitor. The purpose is to provide

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 is an electrical circuit diagram of this embodiment. The amplifier circuit for the high frequency detection output circuit of this embodiment has the same conductivity type and a common emitter type current reversal first amplifier circuit. It has second transistors T□ and T2. Both transistors 'r1. −r2
The bases of are connected to each other. Both transistors T1. +
The base and emitter of the third transistor T3 for base current correction, which has the same conductivity type as T2 and has a common collector type, are connected to the collector and base of the first transistor T1, respectively. (2) is a power signal source, k is a resistor, and OUT is an output terminal.

1st. At the connection point between the bases of the second transistors T□ and T2, there is a capacitor C' for dropping the carrier signal.
One pole of is connected. The other pole of capacitor C' is connected to power supply Vcc. In such a configuration, a peak detection circuit is formed by the third transistor T3 and the capacitor C'. When the signal charged in the capacitor C' is discharged from the capacitor cl, the first. Second transistor T□.

T2 is included in the path of the discharge. Therefore, even if the charging speed of capacitor C' is increased by making the capacitance of capacitor C' very small, the discharging speed will be 1. Since it is about the same as the base current of the second transistors T, , T2, it becomes very low. Therefore, since a peak detection circuit is formed by the third transistor T3 and the capacitor CI, the carrier signal can be dropped.

FIG. 3 is an electric circuit diagram of another embodiment, and FIG.
Portions corresponding to those in the figure are given the same reference numerals. What should be noted in this embodiment is the emitter of the third transistor T3 and the emitter of the first . A resistor for adjusting the time constant is connected between the second transistor T and the connection point between the bases of T2.
is provided.

FIG. 4 is an electric circuit diagram of still another embodiment, and FIG.
Parts corresponding to those in FIG. 3 are given the same reference numerals. What should be noted in this embodiment is a resistor, //, R, which increases the discharge time constant and further enhances the effect of dropping the carrier signal, between the emitters of the first and second transistors T2 and the power supply Vcc. /// is provided.

FIG. 5 is an electric circuit diagram of yet another embodiment, and the first
Portions corresponding to those in FIGS. 4 to 4 are given the same reference numerals.

What should be noted in this embodiment is that a capacitor C// is connected in parallel between the emitter and collector of the third transistor T3;
The configuration of the peak detection circuit together with the transistor T3 is the same as in FIG. 2.

As described above, according to the present invention, the first . One pole of a capacitor is connected to the connection point between the bases of the second transistors, the other pole of the capacitor is grounded in an alternating current manner, and at least a third transistor for base current correction of both transistors and the capacitor are connected to each other. Since the peak detection circuit is constructed by the above, harmonic components can be removed by peak detection even if this capacitor has a small capacity. Therefore, since this capacitor has a small capacity, it becomes possible to integrate the entire circuit element into an IC.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a conventional example, and FIGS. 2 to 5 are electric circuit diagrams of each embodiment of the present invention. T1. T2. T3... 1st. Second. a third transistor;
C'... Capacitor patent applicant ROHM Co., Ltd. agent Patent attorney Kazuhide Okada

Claims (1)

[Claims] (1) The first type has the same conductivity type and has a grounded emitter.
, has a pair of second transistors, the bases of both transistors are connected to each other, and the base and emitter of a third transistor having the same conductivity type as the transistor and having a common collector type are connected to the collector and base of the first transistor, respectively. In the amplifier circuit for a high frequency detection output circuit, one pole of a capacitor is connected to the connection point between the bases of the first and second transistors, the other pole of the capacitor is grounded in an alternating current manner, and at least An amplifier circuit for a high frequency detection output circuit, which comprises a peak detection circuit formed by a third transistor and a capacitor.