JPS58159119A - Reference voltage circuit for cmos integrated circuit - Google Patents

Abstract

PURPOSE:To obtain the reference voltage having high accuracy, by connecting in series a P type MOSFET and an N type MOSFET or a P type MOSFET and >=2N type MOSFETs and using the sum of these threshold voltages. CONSTITUTION:A reference voltage circuit is formed with a reference voltage generating circuit block C and a constant current circuit block D. At the same time, the block C is formed with a P type MOSFET6 and an N type MOSFET7 and 8, and the block D contains a P type MOSFET9, an N type MOSFET10 and a resistance 11. Then VDD-VC=VTH and (VTH=Vth6+Vth7) are satisfied, where VDD is the power supply voltage, VC is the voltage at a point C obtained on the basis of VDD potential, and Vth6 and Vth7 are threshold voltages of MOSFET6 and 7 respectively. Then the reference voltage is formed by the sum of the threshold voltages. Especially it is possible to obtain easily a high level of reference voltage by connecting plural N type MOSFETs in series at the position of the MOSFET7 in the diagram.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention describes how to generate a reference voltage in a reference voltage circuit for a CMO8 integrated circuit.

The conventional method is P-type MQ8FIT, as shown in Figure 1.
The threshold voltage of 1 is used as the reference voltage. Its configuration is a reference voltage generation circuit block Δ and a constant '11t.
It consists of IIt circuit block B.

The mechanism of reference voltage generation can be understood by using the fixed length of the equation below.

In the reference voltage generation circuit block A, if the current flowing from the 11th position of VDD is iα, then ia=”β+m
(VDKI −Va −Vtht )” −・”■ Assuming that the electric potential at 0 length is α, if you design it, voo −va = vth+ −”■.■Formula N VDT) The voltage Vα at point a is P type M
O8FI! It is shown that the threshold of iT1 is satisfied by the l-ruby voltage.

) β1 is the voltage-current conversion rate of P-type M ORF F, V
Dn is 11 voltage, 6a with reference to α VDT) potential.
Yano's senior minister, Vthtke P type M OB FAT 117
``SV9'/@-1'vt1-1voltageThe precision of this reference voltage circuit depends on how to keep the term of the constant current factor α as small as possible from equation 0.

From the constant voltage method circuit block B, find the voltage vh of ha.

If the operation of each MO day FKT is limited to the saturation region and the current flowing baK from the VDD potential is ib, then the P-type MO
The gate voltage of EIFKT 2 is dropped to minus @ of VDD through resistor 5. Also, vbke N type MO8
If the threshold voltage of an N-type MO8FET is □, then Vths = Vt1a, and the length varies as shown in the following formula.

(2) The variation in equation #'1 Van -Va from Vth and t varies depending on voltage #1, even if the voltage dependence due to the VDD IC is ignored in practice. In other words, 0 length is VDD -Vσ=vtn...■noyoden], which matches the idiom, 0-shiki kegi.

Note) β! Voltage-current conversion ratio β of P-type MO8FEIT 2
3/4 is the voltage-current t' conversion ratio of N-type MOEIFET 5.4, Vthx is the threshold voltage of P-type MO8FICT2, and Vths and Vtha are N, respectively.
Type MO8FFT 3.4 threshold t pressure.

Using the above method, it is possible to extract the voltage from the vDD potential of terminal α as a reference voltage.In the case of this method, P type 1%087, which is determined by the substrate concentration, is used.
Only the reference voltage below the threshold voltage of T1 can be used. If a higher voltage is required, it must be amplified using C means such as an operational amplifier, and there may be variations in this process41)! Amplify Kashi Watei Mahe. In this conventional hojo, since the reference voltage was low, the variation was relatively large, and the precision was disadvantageous.

The present invention eliminates such drawbacks, and its purpose is to relatively reduce the deviation by setting a high reference voltage. DIT Based on the example shown in FIG.

The configuration of the reference voltage circuit according to the present invention is similar to that of a reference voltage generation circuit block 0 and a constant current circuit block D.

vrIo If the current flowing to the 11th point and the 0 point is ic, then Note) β・, 1 piece - PwaPsha 1h40SFRT
6. Voltage-current conversion rate of N-type MO8FFT 7, Vt
ha, Vth, and t are threshold voltages of 6 and 7 respectively, and if designed to be smaller by voltages of c and 4 based on CFiVoo potential, then yon-vC-vtm=vtha+vtht=++
+#0). 06) Formula is C based on VDD potential.
, the voltage VC of 6 is P type MO8FICT 6 and N type MO8
It is shown that the sum of the voltages of FhT7 and S5-Ledge-A leads to h i G-.

In this case as well, it depends on how small the constant current XcO term can be kept from the circuit's precision equation. The constant voltage circuit block D is the same as B in FIG. 1, and the gate voltage of the P-type MOflFKT 9 is
1, it is dropped to the minus voltage of the power supply voltage VDD. In addition, the voltage at point d vdij N-type MO81FKT 8
is the gate voltage of Therefore, vTil of VDD-v6
The formula representing the variation from , as in Shunmei in Figure 1, is ij) The voltage dependence due to the variation of f from 77M of VDD -VC can be practically ignored.

In other words, the 0 formula can be changed into a tube shape as follows: +IDD-VC=Vtw...=@, and the 0 formula matches the (b formula).

-6= Note) A#'iP'IJJJMO8FET 9's voltage-current conversion rate, β-mill, β+oFi, respectively N-type MO8F11C
Voltage conversion rate of T8, 10, Vths ke P type MO8F
K79 (r+sv shield voltage.

If you use the above method, P! ! l! The sum of the threshold voltages of the MO8FFT and the NMI MO81FET can be taken as the quasi-voltage fM, but the present invention does not exist in the conventional system shown in FIG. It has another special feature. In other words, as an application of the $2 diagram, as shown in Te931fK '5, one PMMO8FET and an N-type MOP
The problem is that by connecting two or more FBTs in one row, it is possible to extract a higher voltage than the method shown in FIG. 2. Also in the method shown in Fig. 3, the reference voltage is
This is the sum of the threshold voltages of O81FBT. By setting the reference voltage higher in this manner, it becomes possible to further reduce the relative variation.

Examples of the application of the present invention include high voltage circuits such as nine-hour hands, calculators, and the like using 3V lithium batteries.

[Brief explanation of drawings]

Numbers 1, 2, 6, 9, and 12 P-type MO in the figure [1iFF: T5, 4
．． 7.8.10. j3.14.15 tiNWM. PET VDD power supply voltage 5.11ti resistance or more Extractor Suwa Seikosha Co., Ltd. Patent attorney Tomisai Mogami 1 Illustration 2 Figure 3

Claims (1)

[Claims] In CMO8 integrated circuit, P-type MO8FET (M08
Field effect transistors, one each of 1゛1 MO8FET) and 15 MO8FET, and Fip type MO8FE.
1 T and NMI MO8? A reference voltage circuit for a CMO8 integrated circuit, characterized in that two or more ETs are connected in series and the sum of their threshold voltages is used as a reference voltage.