JPH0197075A - Preamplifier circuit for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To completely control clock noise without adjustment by sufficiently reducing the voltage gain of an inversion amplifier circuit only near a clock noise frequency through the use of a filter such as trap in the micro-current amplifier of a feedback type, which feeds back a signal amplified in the inversion amplifier circuit to an input. CONSTITUTION:A titled circuit consists of an image-pickup element 14, the inversion amplifier circuit 11, and feedback circuit 12. When a pulse is impressed on the gate 23 of a MOS transistor 22, the MOS transistor is conducted and a signal load which is photoelectrically converted in a photodiode 21 and the clock noise due to the leakage of the pulse impressed on the gate 23 are impressed on an input terminal 25 and amplified in an amplifier 30. A trap circuit consisting of an inductance 17 and a capacitor 18 removes clock noise components and only signal components are amplified in an amplifier 31 and outputted to an output terminal 24. At the same time, the feedback circuit 12 feeds back a current corresponding to an output signal to the input of the inversion amplifier circuit 11. Consequently, the microcurrent amplifier circuit operates so that it converts only the signal load into the voltage from the input terminal 25.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing circuit for a solid-state imaging device used in a television camera or the like, and particularly to a preamplifier circuit suitable for suppressing clock noise.

[Conventional technology]

2. Description of the Related Art As a copying image device such as a television camera, a solid-state image sensor is used that reads out signal charges accumulated in a plurality of two-dimensionally arranged photodiodes. ! Figure 5 shows an example.

1.2 are horizontal and vertical scanning circuits, respectively.

M for the switch by the pulse output from the scanning circuit
The OS transistors are made conductive according to a certain rule, and the charges accumulated in the photodiodes are sequentially read out.

Regarding the photodiode 3, the pulse outputted from the scanning circuit 2 to the signal line 8 makes the MOS transistors 4 and 6 conductive, and then the signal source 9 from the scanning circuit 1 is turned on.
The MOS transistor 5 is turned on by the pulse outputted to the photodiode 3, and operates to take out the signal charge accumulated in the photodiode 3 onto the video output shaft 7. Therefore, the pulses output from the scanning circuit are unevenly distributed on the video output line via the stray capacitance within the image sensor and the gate capacitance of the MOS transistor, generating spike-like clock noise as shown in FIG. The preamplifier circuit that converts the signal charge taken out on the video output into a voltage must have a dynamic range that is light enough to withstand noise, otherwise the signal component superimposed on it will be distorted. Put it away. However, the upper limit of the dynamic range of the preamplifier circuit is limited by the power supply voltage. Therefore, conventionally, in order to suppress the a-thick noise, a signal similar to the a-thick noise was created and added with the polarity reversed, thereby erasing only one shallow part.

[The problem that the invention attempts to solve]

In the above-mentioned conventional technology, in order to create a signal similar to leakage noise and to eliminate the leakage component with that signal, adjustment is always required, and when there is variation in the leakage component, the above-mentioned The fact that the leakage components cannot be completely eliminated even if optimizing is not sufficiently considered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a preamplifier circuit that can almost completely eliminate leakage components without adjustment even if the leakage components vary.

[Means for solving problems]

The above object is a feedback type minute 't1! which is composed of an inverting amplifier circuit and a feedback circuit which returns the signal amplified by the inverting amplifier circuit to the input KNI! This is achieved by using a filter such as a trap in the L-flow amplifier circuit and making the voltage gain of the inverting amplifier circuit sufficiently small only in the vicinity of the a noise frequency.

[Effect]

The transfer impedance of a feedback type micro current amplifier circuit in which the voltage gain of the inverting amplifier circuit is sufficiently small only near the noise frequency becomes a large transfer impedance with respect to the signal component of the video output, as shown in Figure 6. , the transfer impedance is sufficiently small for clock noise components. As a result, only the signal component on the video output is converted to voltage.

As a result, clock noise is suppressed after the amplification stage into which the trap is inserted, and saturation of the inverting amplification circuit due to such a clock noise can be prevented.

This method does not cause oscillation due to sudden changes in phase. We also discovered that there were no problems with image quality in a video camera using the microcurrent amplification circuit. Next, the reason why oscillation does not occur due to a sudden change in phase will be explained using FIG. 14 is an image sensor, 11 is an inverting amplifier circuit, 12 is a feedback circuit, 10
13 represents a voltage-controlled current source, 13 represents a positive phase amplifier, and 21 represents a photodiode. Loop gain μ of the minute current amplification circuit composed of the inverting amplification circuit 11 and the reduction circuit 12
When β is expressed using the symbols in the figure, Cin''>> C1, 1s ωc6nRj)'ct: @J
When j, equation (1) becomes. Furthermore, when this equation (C) is converted to mW, it becomes. The case where the imaginary part of equation (5) becomes 0 is ω=0 or −C
CL-CJRIR)=1. When ω=0, the loop gain μβ is μβ−−G from the equation (tl), which also does not cause oscillation. Therefore, even if a trap is inserted, oscillation will not occur.

In addition, if a trap is provided at the output end of the volatile element and a noise is removed from the output of the image sensor, the voltage between the trap insertion point and the minute current amplification circuit output at the resonant frequency tL of the trap, the vll gain, is large. , a large noise is generated in the output of the micro-current loudspeaker circuit at the resonance no wave number.

However, by inserting a trap inside the inverting amplifier circuit, it is possible to suppress clock noise without generating large noise at the common frequency of the trap, and it is possible to reduce the dynamic range required for the inverting amplifier circuit.

Transfer impedance Z of the minute current N@circuit shown in Figure 5
(ω) is shown in FIG. The cutoff frequency is m, and the frequency characteristic is such that the transfer impedance becomes extremely small at 8. Further, m and h can be expressed by equation (41(5)).

j・=2, surface °(51) In this way, by making the voltage gain of the inverting amplifier circuit sufficiently small only in the vicinity of clock noise @ wave number, clock noise can be suppressed and saturation of the inverting amplifier circuit due to clock noise can be prevented. It is possible to realize a minute tm amplification circuit.

[Embodiments of the invention]

Hereinafter, an embodiment of Brown 1 of the present invention will be explained with reference to Fig. 1.

The first effect is the fR image element 14 and the inverting amplifier circuit 11.
, and a fin feedback circuit 12, the output of the image sensor 14 is connected to the input terminal 25 of the inverting amplifier circuit 11 and the output 1c of the feedback circuit 12, and the output of the inverting amplifier circuit 11 is connected to the output terminal 24 and the feedback circuit 120 input. It is connected to the. The inverting amplifier circuit 11 connects the input of the amplifier 310 to the input terminal 25 and connects the output of the error amplifier 30 to the input of the amplifier 51 via the resistor 52 . The width amplifier 310 input is connected to a reference potential through a series circuit of an inductance 17 and a capacitor 18,
The output of the amplifier 31 is connected to the output terminal 24. The feedback circuit 12 connects a parallel circuit of 10,000'' of a feedback resistor 20 and a feedback capacitor 19 to the input of the inverting amplifier circuit 110, and the other to the input of the inverting amplifier circuit.The operation of this embodiment will be explained as follows.
When a pulse is applied to the gate 25 of the MOS transistor 22, the MOS transistor 22 becomes conductive, and the signal charge photoelectrically converted by the photodiode 21 and the clock noise caused by the pulse impressed on the gate 25 are transferred to the input terminal. 25. These two signals are sent to the amplifier 3
After being amplified by 0, inductance 17 and capacitor 1
The trap circuit consisting of 8 removes the clock noise component, and only the signal component is amplified by the amplifier circuit 31. When an output voltage is applied to the output terminal 24, the current corresponding to the output signal is inverted and amplified by the feedback circuit 12. It is fabricated to feed back to the circuit 110 input. This operation is performed by the inverting amplifier circuit 11
Focusing on the transfer impedance of the minute current amplification circuit constituted by the circuit 12 and the navigation circuit 12, the transfer impedance is large for signal components and sufficiently small for clock noise components. That is, the minute current amplification circuit operates to convert only the signal charge from the input terminal 25 into a voltage. According to this embodiment, since no cancellation circuit is used, the non-alias noise can be completely suppressed, and this suppression effect does not change even if the waveform of the noise changes.

Furthermore, since clock noise, which is several ten times as large as the signal component, is suppressed at the input of the amplifier 31, it is possible to reduce the dynamic range of the amplifier 31.

A second embodiment of the present invention will be described using FIG. 2. Second
In the embodiment, in the first embodiment, the inverting amplifier circuit 11
is a specific circuit, and the feedback circuit 12 is further provided with a filter that effectively reduces the feedback capacitance 19. The inverting amplifier circuit connects the gate of the common source FET 54 to the input terminal 25, and connects the source to an appropriate voltage source 36.
, its drain is connected to the emitter of the common base transistor 37, and the resistor 35 is connected to a suitable voltage source 49. The base and collector of common base transistor 370 are connected to a suitable voltage source 39 and the base of common emitter transistor 430, respectively. Furthermore, the collector of the common base transistor 57 is connected to a resistor 59.
It is connected to the reference voltage via the inductor 17 and directly read to the reference potential via the series circuit of the inductance 17 and the capacitor 18. The emitter and collector of common emitter transistor 43 are connected to a reference potential and a suitable voltage source 49 via resistor 42 and resistor 44, respectively.

Furthermore, the collector of the emitter resistance transistor 43 is
The emitter of the base resistance transistor 37 is connected to the input of an amplifier 45 through a parallel circuit of a resistor 40 and a capacitor 41, and the output of the amplifier 45 is connected to the output terminal 24.

The feedback circuit 12 has one of the parallel circuits of the feedback resistor 20 and the feedback capacitor Ji19 connected to the input of the inverting amplifier circuit 11, and the other connected to the resistor 4.
8 to the output of the inverting amplifier circuit 11, and a resistor 46 and a capacitor 47 from the connection between the feedback resistor 20 and the resistor 48.
connected to the reference potential through a series circuit of The feedback circuit 1
2 is effectively equivalent to a parallel circuit in which R1, that is, the resistor 48 is adjusted to vI4 so that (to CR1+ using the symbol in the figure) C value = C1Ri, and is equivalent to the parallel circuit in the feedback circuit 12 in the first embodiment. It's the same. The inverting amplifier circuit 11 amplifies the signal applied to the input terminal 25 using a source-common FET 54 and a base-common transistor 57, and then removes a noise component using a trap circuit consisting of an inductance 17 and a capacitor 18, and converts the signal component into a amplifier 4
It is amplified by 5. Note that the feedback by the resistor 40 and capacitor 41 is provided for phase compensation of the inverting amplifier circuit 11, and a capacitor may be provided in parallel with the resistor 42, or the amplifier 45 may be configured with a first-order a-path characteristic. good. This embodiment is the same as the embodiment of Series 1, and the same effects can be obtained.

〔Effect of the invention〕

According to the present invention, since there is no need to use a cancellation circuit, noise can be completely suppressed without adjustment, and the naturalness is greatly improved. Furthermore, the same effect can be obtained on enemies whose waveforms of crack noise vary, and the dynamic range required for the microcurrent amplification circuit can be reduced.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of the first embodiment of the present invention, Figure 2 (2) is a circuit diagram of the second embodiment of the present invention, Figure R3 is a circuit diagram of the photographing device, and Figure 4 is a circuit diagram of the second embodiment of the present invention. Figure 5 is an equivalent circuit diagram of the preamplifier circuit, and Figure 6 is a characteristic diagram showing transfer impedance. 11... Inverting amplifier circuit 12... Feedback circuit 14
...Image sensor closed Figure 1 Figure 2 Diagram porridge (r Cy J'V Ye 44 Figure 45 Figure 6 Figure 6 Circular jL&j

Claims (1)

[Claims] 1. Collecting signal charges from a solid-state imaging device that has a plurality of photoelectric conversion elements arranged in a two-dimensional manner, a switch element that transmits detection signals from the photoelectric conversion elements, and a scanning circuit that sequentially applies scanning pulses to the switch elements. For use in a solid-state imaging device, the preamplifier circuit for read amplification comprises an inverting amplifying circuit, a feedback circuit, and a filter means, and the filter means reduces the voltage gain of the inverting amplifying circuit only near the leakage clock noise frequency. preamplifier circuit.