CN104199501A - High-output impedance current source circuit - Google Patents

Abstract

The invention provides a high-output impedance current source circuit, and belongs to the field of integrated circuits. The high-output impedance current source circuit comprises a current source generation circuit composed of a triode Q1 and a resistor R1, a negative feedback circuit composed of an operational amplifier AMP1 and an NMOS N1 and used for increasing output impedance and a common source electrode circuit composed of an NMOS N2. According to the high-output impedance current source circuit, a traditional NMOS is replaced by the high-output impedance triode, the method that the negative feedback circuit and the common source electrode circuit with the source electrode negative feedback are connected with a current source generation circuit in series is adopted, the output impedance of a current source is increased greatly, and stability of the current source is improved.

Description

A kind of high output impedance current source circuit

Technical field

The invention belongs to integrated circuit fields, particularly a kind of high output impedance current source circuit.

Background technology

Current source circuit is the important component part in Analogous Integrated Electronic Circuits, has demand widely in Analogous Integrated Electronic Circuits.The output impedance of current source is the important parameter of current source circuit, and output impedance is higher, shows that current source output current is more stable.Therefore,, in high-precision circuit, particularly, in current steer type DAC, it is extremely important that the current source circuit of high output impedance just seems.

The output impedance of common current source is generally the megohm order of magnitude, and electric current output is stable not, so common current source output impedance is difficult to meet the requirement of high-precision circuit.The most conventional way is at current source output impedance R ₀extra resistance R of upper series connection ₁, make total output impedance by original R ₀be increased to R ₀+ R ₁.But this way needs very large chip area, and can consume larger voltage remaining.So above-mentioned way increases the limited in one's ability of current source output impedance.

Summary of the invention

In view of this, the invention provides a kind of high output impedance current source circuit, to improve the output impedance of current source circuit.

A high output impedance current source circuit, comprises electric current source generating circuit, for improving the negative-feedback circuit of output impedance and with the common-source circuits of source negative feedback; Electric current source generating circuit is comprised of triode Q1 and resistance R 1, for improving the negative-feedback circuit of output impedance, operational amplifier A MP1 and NMOS pipe N1, consists of, and manages N2 form with the common-source circuits of source negative feedback by NMOS; Resistance R 1 one end ground connection, the other end is connected to the emitter of triode Q1; Triode Q1 base stage meets input pin VBIAS, and the source electrode of collector and NMOS pipe N1 joins and receives the negative input end of operational amplifier A MP1; The positive input termination reference voltage input VREF1 of operational amplifier A MP1, the output of operational amplifier A MP1 connects the grid of NMOS pipe N1; The drain electrode of NMOS pipe N1 connects the source electrode of NMOS pipe N2; The grid of NMOS pipe N2 meets reference voltage input VREF2, and drain electrode meets current output terminal IOUT.

Further, described operational amplifier A MP1 is one-level operational amplifier.Wherein, the source electrode of PMOS pipe P11 meets power vd D, and grid and drain electrode are joined, and receives the drain electrode of grid and the NMOS pipe N11 of PMOS pipe P12; The source electrode of PMOS pipe P12 meets power vd D, and drain electrode meets the output VOUT of operational amplifier A MP1; The grid of NMOS pipe N11 meets the positive input terminal INP of operational amplifier A MP1, and source electrode connects the NMOS pipe source electrode of N12 and one end of resistance R 11; The other end ground connection of resistance R 11; The grid of NMOS pipe N12 meets the negative input end INN of operational amplifier A MP1, and drain electrode meets the output VOUT of operational amplifier A MP1.

High output impedance current source circuit provided by the invention, by using the triode of high output impedance to substitute traditional NMOS, manage, and use negative-feedback circuit and with the method for the common-source circuits of source negative feedback, the output impedance that has greatly improved current source, has strengthened the stability of current source.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is high output impedance current source circuit figure provided by the invention.

Fig. 2 is the internal circuit diagram of operational amplifier A MP1 in high output impedance current source provided by the invention.

Fig. 3 is that in high output impedance current source circuit provided by the invention, current source produces circuit theory diagrams.

Fig. 4 is for improving the negative-feedback circuit schematic diagram of output impedance in high output impedance current source circuit provided by the invention.

Fig. 5 is with the common-source circuits schematic diagram of source negative feedback in high output impedance current source circuit provided by the invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.

A high output impedance current source circuit, as shown in Figure 1, comprises electric current source generating circuit, for improving the negative-feedback circuit of output impedance and with the common-source circuits of source negative feedback; Electric current source generating circuit is comprised of triode Q1 and resistance R 1, for improving the negative-feedback circuit of output impedance, operational amplifier A MP1 and NMOS pipe N1, consists of, and manages N2 form with the common-source circuits of source negative feedback by NMOS; Resistance R 1 one end ground connection, the other end is connected to the emitter of triode Q1; Triode Q1 base stage meets input pin VBIAS, and the source electrode of collector and NMOS pipe N1 joins and receives the negative input end of operational amplifier A MP1; The positive input termination reference voltage input VREF1 of operational amplifier A MP1, the output of operational amplifier A MP1 connects the grid of NMOS pipe N1; The drain electrode of NMOS pipe N1 connects the source electrode of NMOS pipe N2; The grid of NMOS pipe N2 meets reference voltage input VREF2, and drain electrode meets current output terminal IOUT.

Described operational amplifier A MP1 is one-level operational amplifier.As shown in Figure 2, INP is the positive input terminal of operational amplifier A MP1 to its structure, and INN is the negative input end of operational amplifier A MP1, and VOUT is the output terminal of operational amplifier A MP1.Wherein, the source electrode of PMOS pipe P11 meets power vd D, and grid and drain electrode are joined, and receives the drain electrode of grid and the NMOS pipe N11 of PMOS pipe P12; The source electrode of PMOS pipe P12 meets power vd D, and drain electrode meets the output VOUT of operational amplifier A MP1; The grid of NMOS pipe N11 meets the positive input terminal INP of operational amplifier A MP1, and source electrode connects the NMOS pipe source electrode of N12 and one end of resistance R 11; The other end ground connection of resistance R 11; The grid of NMOS pipe N12 meets the negative input end INN of operational amplifier A MP1, and drain electrode meets the output VOUT of operational amplifier A MP1.

Described electric current source generating circuit as shown in Figure 3, resistance R 1 one end ground connection, the emitter of another termination triode Q1; The base stage of triode Q1 meets bias voltage providing end VBIAS, and collector meets current output terminal IOUT1.Electric current source generating circuit is carried out to small-signal analysis, can show that its output impedance of seeing into from IOUT1 is: the introducing of resistance R 1 makes triode output resistance r _q1increased I _c1r ₁/ V _tdoubly, V wherein _tbe the constant that a size is about 26mV, I _c1for by the electric current of transistor collector.

Described for improve output impedance negative-feedback circuit schematic diagram as shown in Figure 4, resistance r _o1for the output impedance of the source generating circuit of electric current shown in Fig. 3, one end ground connection, another termination NMOS pipe source electrode of N1 and the negative input end of operational amplifier A MP1; The positive input termination reference voltage V REF1 of operational amplifier A MP1; The grid of NMOS pipe N1 connects the output terminal of operational amplifier A MP1, and drain electrode meets current output terminal IOUT2.Fig. 4 circuit is carried out to small-signal analysis can be drawn: r _o2=A ₁g _mn1r _on1r _o1, A wherein ₁for the gain of operational amplifier A MP1, g _mn1for the mutual conductance of NMOS pipe N1, r _on1for the output resistance of NMOS pipe N1, r _o1output impedance for the source generating circuit of electric current shown in Fig. 3.

The described common-source circuits with source negative feedback as shown in Figure 5, r wherein _o2for Fig. 4 is for improving the output impedance of the negative-feedback circuit of output impedance.R _o2one end ground connection, the source electrode of another termination NMOS pipe N2; The grid of NMOS pipe N2 meets reference voltage V REF2, and drain electrode meets output VOUT.The common-source circuits with source negative feedback shown in Fig. 5 is carried out to small-signal analysis can be drawn: output impedance r _o3=(1+g _mn2r _o2) r _on2; Wherein, g _mn2for the mutual conductance of NMOS pipe N2, r _o2for for improving the output impedance of the negative-feedback circuit of output impedance, r _on2output resistance for NMOS pipe N2.

According to above-mentioned analysis, can draw, total output impedance of high output impedance current source circuit of the present invention is $R_{\mathrm{OUT}}=r_{o3}=[r_{q1}(1+\frac{I_{C1}{R}_1}{V_T})*A_1{g}_{\mathrm{mn}1}{r}_{\mathrm{on}1}*g_{\mathrm{mn}2}+1]*r_{\mathrm{on}2;}$ Wherein, r _o3for the output impedance of the common-source circuits with source negative feedback shown in Fig. 5, r _q1for triode output resistance, I _c1for by the electric current of transistor collector, V _tbe the constant that a size is about 26mV, A ₁for the gain of operational amplifier A MP1, g _mn1for the mutual conductance of NMOS pipe N1, r _on1for the output resistance of NMOS pipe, g _mn2for the mutual conductance of NMOS pipe N2, r _on2output resistance for NMOS pipe N2.

By above-mentioned analysis, can obviously be drawn, high output impedance current source circuit provided by the invention, by using the triode of high output impedance to substitute traditional NMOS, manage, and use negative-feedback circuit and with the method for the common-source circuits of source negative feedback, greatly increase the output impedance of current source, improved the stability of current source.

In this instructions, each embodiment adopts the mode of going forward one by one to describe, and each embodiment stresses is the difference with other embodiment, between each embodiment identical similar part mutually referring to.

Above-mentioned explanation to the disclosed embodiments, makes professional and technical personnel in the field can realize or use the present invention.To the multiple modification of these embodiment, will be apparent for those skilled in the art, General Principle as defined herein can, in the situation that not departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention will can not be restricted to these embodiment shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.

Claims (2)

1. a high output impedance current source circuit, is characterized in that: comprise electric current source generating circuit, for improving the negative-feedback circuit of output impedance and with the common-source circuits of source negative feedback; Electric current source generating circuit is comprised of triode Q1 and resistance R 1, for improving the negative-feedback circuit of output impedance, operational amplifier A MP1 and NMOS pipe N1, consists of, and manages N2 form with the common-source circuits of source negative feedback by NMOS; Resistance R 1 one end ground connection, the other end is connected to the emitter of triode Q1; Triode Q1 base stage meets input pin VBIAS, and the source electrode of collector and NMOS pipe N1 joins and receives the negative input end of operational amplifier A MP1; The positive input termination reference voltage input VREF1 of operational amplifier A MP1, the output of operational amplifier A MP1 connects the grid of NMOS pipe N1; The drain electrode of NMOS pipe N1 connects the source electrode of NMOS pipe N2; The grid of NMOS pipe N2 meets reference voltage input VREF2, and drain electrode meets current output terminal IOUT.

2. high output impedance current source circuit as claimed in claim 1, is characterized in that, described operational amplifier A MP1 is one-level operational amplifier, wherein, the source electrode of PMOS pipe P11 meets power vd D, and grid and drain electrode are joined, and receives the drain electrode of grid and the NMOS pipe N11 of PMOS pipe P12; The source electrode of PMOS pipe P12 meets power vd D, and drain electrode meets the output VOUT of operational amplifier A MP1; The grid of NMOS pipe N11 meets the positive input terminal INP of operational amplifier A MP1, and source electrode connects the NMOS pipe source electrode of N12 and one end of resistance R 11; The other end ground connection of resistance R 11; The grid of NMOS pipe N12 meets the negative input end INN of operational amplifier A MP1, and drain electrode meets the output VOUT of operational amplifier A MP1.