JPH03216031A - Amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier device used as a preamplifier device for optical communications.

[Conventional technology]

FIG. 4 shows a preamplifier used in conventional optical communications.

This amplifier is single-ended! \stomach? This is a circuit in which a bias resistor R is connected to the input terminal 1 side of the impedance type amplifier 3 so that an output signal is obtained from the output terminal 2. Specifically, for example, the 1989 Institute of Electronics, Information and Communication Engineers Spring National Conference Lecture No. A circuit as shown in FIG. 5 shown in FIG. 1 of C-414 is known. In this circuit, an optical signal is received by a bin diode 4, and the resulting signal is amplified by a FETQ1■ to obtain an output signal from an output terminal 2. At this time, a desired bias point is determined by applying a bias via a load resistor R connected to the drain of FET Q1 and a resistor RL connected to the gate.

[Problem to be solved by the invention]

However, such an amplifier has only one amplifier, and once the bias point is determined, various characteristics such as transimpedance-frequency characteristics are uniquely determined, and the same amplifier cannot be used for different purposes. For example, wideband amplification of an optical receiver requires an amplification device with a wide band, and a low-noise preamplifier requires an amplification device with a narrow bandwidth but low noise. However, with the conventional amplifying device described above, it has not been possible to realize such different characteristics with a single device.

SUMMARY OF THE INVENTION An object of the present invention is to provide an amplifying device that realizes different characteristics even though the amplifying device has the same configuration, and thereby allows the same device to handle amplification for different uses.

[Means to solve the problem]

The amplifier device according to the present invention includes a differential amplifier having two input terminals, a first bias resistor connected to one of these input terminals, and having a resistance value different from the first bias resistor. and a second bias resistor connected to the other of the input terminals.

[Effect]

Since the amplifier device according to the present invention is configured as described above,
The human power impedance of the two amplifier circuits that make up the differential amplifier will differ, and there is a difference between applying an input signal to one input terminal of the differential amplifier and using the other input terminal as a reference, and vice versa. When one input terminal of a dynamic amplifier is used as a reference and an input signal is applied to the other input terminal, the dynamic amplifier acts as two amplifier devices with different input impedances, that is, with different characteristics.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An amplifier device according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 3 of the accompanying drawings.

FIG. 1 shows a configuration diagram of an amplifier device according to an embodiment of the present invention. In this embodiment, in an amplifier 100 including a differential amplifier whose input terminals are 101A and IOIB and whose output terminals are 102A and 102B, a bias resistor Rb1 is connected to the input terminal 101A, and the bias resistor Rb1 is connected to the input terminal 101B. A bias resistor Rb2 having a different resistance value from b1 is connected. Here, the bias resistances R and R are, for example,
bl b2 Rb1>Rb2.

In an amplification device having such a configuration, an input signal is applied to the input terminal 101A and the input terminal 101B is used as a reference, or a human input signal is applied to the input terminal 101B and the input terminal 101A is used as a reference. In either case, the output signal is obtained from the output terminal 102A, for example. A differential amplifier is a pair of two amplifier circuits, and since the bias resistors R and H have different values bl b2 , each amplifier circuit has a different human impedance. The two paired amplifier circuits are independent and have different characteristics.

FIG. 2 shows a circuit diagram according to an embodiment of the present invention suitable for IC implementation. In this figure 2, FETQ,Q
are a pair of amplifier circuits and constitute a differential amplifier. FETQ. 1 at the drain of Q3 is FET Q2 whose gate and source are shorted, respectively.
Q4 is connected and constitutes a constant current load. F
FETQ5, which is a constant current source whose gate and source are short-circuited, is connected to the sources of ETQ and Q3. The above FETs Q1 to Q5 constitute a differential amplifier that operates differentially. In other words, FETQ,
A signal corresponding to the difference in signal 1 input to the gate of Q3 is amplified.

FETs Q and Q constitute 68 buffer stages for each output signal of the differential amplifier. In other words, the signal is guided from one output point of the differential amplifier to the gate of FET Q6, outputted from the source to achieve low output impedance, level-shifted to the required voltage by level shift diode D1, and then transferred between the gate and source. The above signal is sent to a constant current load consisting of FET Q7 which is short-circuited. Here, the drain of FETQ7 is connected to the output terminal 102A. Similarly, regarding the signal at the other output point of the differential amplifier,
to F8 ETQ via level shift diode D2. Connect the drain of FETQ9 to the output terminal 102B. FETQ,Q,QB
, 24 Q is connected to a power supply of voltage VDD, and the sources of 8 FETQ, Q, Q9 are connected to 5 of voltage V
7
An ss power source is connected to provide driving power for the amplifier. Bias resistor Rb1 is input terminal 10
1A and a bias resistor R. ．． J2 is human power terminal 1
Connected to 01B.

In this example, the gate voltage of FETQ-Q9 is set to -1V, and the gate width of each gate is set to 150μm, 175μm, 1150μm, 175μm.
μm, 150μm, 150μm1150μm, 150μm
Bias resistance R set to m, 150 μm, 150 μm
, R are 2KΩ and IKΩ, respectively.

The input terminal 101A of the amplifier device having such a configuration. 101
B is the input terminal, and the photodiode (capacity 0
．． FIG. 3 shows the results of an AC (alternating current) analysis when a 65 pF) is connected between the input terminal 101A (IOIB) and VDD as shown in FIG. In either case, the output terminal 102A is used. In FIG. 3, ■ indicates a transimpedance-frequency response characteristic when a photodiode is connected to the input terminal 101A, and ■ indicates a transimpedance-frequency response characteristic when a photodiode is connected to the human power terminal 101B. In addition, these results can be summarized as follows.

From these, bias resistor Rb1 (
-2KΩ), it is possible to realize an amplifier device with a large transimpedance and a narrow band, and by using the bias resistor Rb2 (-1KΩ), which has a smaller resistance value, it is possible to realize an amplifier device with a small transimpedance but a wide band.

Therefore, among preamplifiers for optical receivers, when a wide dynamic range is required, such as a wideband preamplifier, an amplifier device having a small bias resistance is configured by using the input terminal 101B as an input terminal and using the bias resistor Rb2. In this way, broadband characteristics can be obtained. Also, as a low-noise preamplifier, the manual terminal 101
By using A as a human input terminal, an amplifier device having a larger bias resistance than the bias resistor Rbl may be configured to obtain a narrow band but low noise characteristic.

Note that if the bias resistors R and R are externally attached, bl
b2 Can be flexibly adapted to various circuits.

〔Effect of the invention〕

As described above in detail, according to the present invention, the bias resistances at the two input terminals constituting the differential amplifier are made different, so that the input impedance is different, so that the device has different characteristics depending on the selection of the input terminals. Therefore, it can be used for amplification of different purposes even though only one amplification device is used.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an amplifier according to an embodiment of the present invention, FIG. 2 is a circuit diagram of an amplifier according to an embodiment constructed using FETs, and FIG. 3 is a circuit diagram of an amplifier according to an embodiment of the present invention. Figures 4 and 5 showing frequency response characteristics are block diagrams of conventional amplifier devices. 100...Amplifier, IOIA. IOIB...Manual terminal, 102A, 102B...Output terminal, Q-Q
・・・FET, R, R ・・・Bias resistance, 1
9 bl
b2D, D...Level shift diode. l2

Claims (1)

[Claims] A differential amplifier having two input terminals, a first bias resistor connected to one of the input terminals, and the input terminal having a resistance value different from the first bias resistor. and a second bias resistor connected to the other one of the bias resistors.