JPS6329847B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is suitable for application to a DC current amplifier such as a tuning meter, and absorbs variations in the DC current amplification factor of transistors and also reduces variations in operating point. The present invention relates to a current amplification circuit configured as described above.

Conventionally, a current amplification circuit implemented as an IC is configured as shown in Figure 1. In order to minimize variations in output current due to changes in the DC current amplification factor (usually 50 to 300), the base of transistor 2 is As the resistor 4 connected in series with the bias supply power source 3, a pinch resistor as shown in FIG. 2 may be used, which changes in accordance with the DC current amplification factor _hFE . still,
As is well known, the pinch resistance is formed by forming a P-type semiconductor base diffusion region 7 in an N-type semiconductor epitaxial layer 6 grown on a P-type semiconductor substrate 5, for example.
An emitter diffusion region 8 of an N-type semiconductor is formed in this base diffusion region 7, and a resistor is formed in a portion of the base diffusion region 7 having a width W sandwiched between the epitaxial layer 6 and the emitter diffusion region 8. , resistance lead-out terminals 9 and 10 are connected to both ends of the base diffusion region 7. Note that 6' and 6'' are separation layers.
This is also part of the structure of the transistor, and in the case of a transistor, its DC current amplification rate
_hFE is mostly determined by the width W of the base diffusion region 7.

When constructing a direct current amplification circuit by applying the basic circuit shown in FIG. 1, the connections shown in FIG. 3 can be considered. That is, the collector of a transistor 12 having a diode 11 connected between its base and emitter is connected to the power supply +B through a pinch resistor 13.
In this circuit, since the resistor 13 is formed of a pinch resistor as described above, the DC current amplification factor h _FE of another transistor formed simultaneously on the same semiconductor substrate 5 as the resistor 13 is When the variation in is used as a parameter, the characteristics of the input current I and the maximum output current I _O change as shown by the solid line in FIG. On the other hand, when the resistor 13 is replaced with a diffused resistor, the I- _IO characteristics change as shown by the broken line. Therefore, for example, tuning meter 1
7 is connected between the power supply +B and the terminal 16 to which the collector of transistor 2 is connected to facilitate the so-called tuning operation, the characteristics of the input signal voltage (dB) and the maximum output current I _O are as follows: As the width factor h _FE changes, it varies as shown in FIG. 5. Incidentally, FIG. 6 shows an example of a diffused resistor, in which an N-type semiconductor substrate 5 is formed on a P-type semiconductor substrate 5 in substantially the same manner as the pinch resistor shown in FIG.
A P-type semiconductor base diffusion region 7 is formed in the P-type semiconductor epitaxial layer 6, and resistance lead-out terminals 9 and 10 are connected to both ends of the P-type semiconductor base diffusion region 7.

In view of this, the present invention eliminates the above-mentioned drawbacks, is suitable for application to tuning meters, etc., and absorbs variations in the DC current amplification factor h _FE and also reduces variations in the operating point. The purpose of this paper is to propose a current amplification circuit as described above.

An embodiment of the current amplification circuit according to the present invention will be described in detail below with reference to FIGS. 7 to 9, and parts corresponding to those in FIGS. 1 to 6 described above are given the same reference numerals. The redundant explanation will be omitted.

The current amplification circuit according to the present invention constitutes a current mirror circuit MK to which a current corresponding to an input signal is supplied, and a transistor 1 forming this circuit MK.
1 pinch resistor on the collector and emitter of 2, respectively.
3 and 14, and this first transistor 12
The output current taken out from the collector of the current mirror circuit MK is supplied to the base of the second transistor 2 as a drive current, and the pinch resistors 13 and 14 of the current mirror circuit MK, the first transistor 12, and the second transistor 2 are manufactured on the same semiconductor substrate.

That is, in FIG. 7, the base of the first transistor 12 to which the signal under test is supplied via the input terminals 1a and 1b is grounded via the diode 11 and the current limiting diffused resistor 4, and the collector is connected to the second transistor 12. It is connected to the base of the transistor 2 and connected to the power supply +B via the pinch resistor 13 in the same manner as described above, and its emitter is grounded via the pinch resistor 14.
The collector of the second transistor 2 is connected to the tuning meter connection terminal 16, its emitter is directly grounded, and the tuning meter 17 is connected between the terminal 16 and the power supply +B.

According to the configuration described above, the first transistor 1
2, second transistor 2 and pinch resistor 13,
14 are manufactured on the same semiconductor substrate,
A diode 1 is connected to the base of the first transistor 12.
1, a pinch resistor 13 is connected to its collector, and a pinch resistor 14 is connected to its emitter, so that the direct current amplification factor h _FE of the transistors formed on the same substrate is Even when the resistance value varies, the ratio of the resistance values of the pinch resistors 13 and 14 remains constant, and the ratio of the pinch resistor 14 to the diffused resistor 4 changes, so that the input current I and the maximum output current I _O The characteristics of h _FE do not vary much as shown in Figure 8 even when FE changes, and in the same way, input signal strength (dB) and maximum output current I _O
Even if h _FE changes, the characteristics do not vary much as shown in Figure 9.

Furthermore, if the h _FE of the second transistor 2 increases, the resistance values of the pinch resistors 13 and 14 also increase;
The gain of the current mirror circuit MK constituted by 1 becomes small, and as a result, a large amount of base-emitter current flows through the second transistor 2, and the second transistor 2 becomes more conductive. In addition, the pinch resistor 13 is connected to the maximum output current I _O of the second transistor 2,
That is, the maximum current of the tuning meter (not shown) is determined.

Thus, according to the current amplification circuit according to the present invention, by forming the pinch resistor and the first and second transistors on the same semiconductor substrate, the width W of the base diffusion region can be made smaller than that of the individual ICs. can be regulated to the same width, and the DC current amplification rate is
Since a resistance value corresponding to h _FE can be obtained, variations in the input current - maximum output current characteristics due to variations in the DC current amplification factor of individual ICs during IC manufacturing can be suppressed as much as possible. It is also possible to reduce variations in operating points.

The current amplification circuit according to the present invention can be easily used as a tuning meter driving circuit by connecting the meter to the collector side of the second transistor and supplying the input signal to be measured to the base side of the first transistor. Of course, the present invention is not limited to the above-mentioned example, but can be easily applied to various other examples.

[Brief explanation of the drawing]

Fig. 1 is a basic circuit diagram of a conventional current amplification circuit, Fig. 2 is a cross-sectional view of the pinch resistor in Fig. 1, Fig. 3 is a circuit diagram of a conventional current amplification circuit, and Fig. 4 is a diagram of Fig. 2. Figure 5 is a characteristic curve diagram of input current vs. maximum output current, Figure 5 is a characteristic curve diagram of input signal voltage vs. maximum output current in Figure 2, Figure 6 is a cross-sectional diagram of the diffused resistor in Figure 2, and Figure 7 is A circuit diagram of an example of a current amplification circuit according to the present invention, FIG. 8 is a characteristic curve diagram of the input current-maximum output current of FIG. 7, and FIG.
FIG. 3 is a characteristic curve diagram of input signal voltage versus maximum output current in the figure. 2 is a second transistor, 12 is a first transistor, 13 and 14 are pinch resistors, and MK is a current mirror circuit.

Claims (1)

[Claims] 1 A resistor is connected to the emitter and collector of the first transistor, and a diode is provided to the base to supply a bias voltage substantially equal to the base-emitter voltage of the first transistor, and the current of the diode is limited. A current amplification circuit comprising: a current mirror circuit to which a resistor is connected, an input signal is supplied to the base and a corresponding signal is output from the collector; and a second transistor to which the output signal is supplied. , the resistor connected to the emitter and collector of the first transistor is formed of a pinch resistor,
The current increasing device is characterized in that the resistor for limiting the current of the diode is formed of a diffused resistor, and the first and second transistors and the respective pinch resistors are manufactured on the same semiconductor substrate. Width circuit.