JPS61286771A - Method for analyzing semiconductive integrated circuit - Google Patents

Abstract

PURPOSE:To perform setting so that an entire image having non-linear characteristics corresponds to gain calculation and to make it possible to rapidly and accurately perform the planning of a high-degree electronic circuit, by standardizing the change component of the value of the current flowing to each collector of the input transistor of a differential amplifying circuit to set a modulation degree. CONSTITUTION:The bias current in the side of the common emitter of the input transis tor of a differential circuit is set to 2Io. The change component DELTAI(=Ic-Io) of the complemented current obtained in the collector side of an input transistor when input was applied between the basis terminals of said transistor is standardized by dividing the same by the current Io having no change component appearing in each collector side when a zero signal was applied between the base terminals to set a modulation degree alpha(-1<=alpha<=1). The input voltage Vin of the differential circuit is expressed as a form of logarithmic function (Vin=alnalpha+b) by using the modulation degree alphaand, when the quantitative data of the differential circuit is desired to be obtained at the time of the planning of a circuit, the data is calculated by the calculation of the numerical value based on a relational equation and the relational equation is drawn on an x, y plane to draw non-linear characteristics.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for analyzing semiconductor integrated circuits, particularly a method for analyzing a differential amplifier type circuit network. By making it correspond to , its operating characteristics can be visually expressed, and circuit network analysis and, by extension, its design can be easily performed.

[Conventional technology]

In semiconductor integrated circuits, a differential amplifier circuit is a universal basic circuit unit, and simplicity and understandability are important in circuit network analysis.

Figure 9 shows a differential amplification circuit. Signal source (
voltage value Vin), 5.5 is an input transistor (Q, also written as >, 10
．． 11 is the load resistance (resistance value RLI, RLt), 12
．． 13 is an output terminal (also written as T3°T4), and 14 is a power supply (voltage value V B2).

In this differential amplifier circuit, for example, an equivalent circuit is used when calculating a gain. FIG. 10 shows the small signal equivalent circuit of FIG. 9, and in the figure, 15.
Reference numeral 16 indicates the base resistance of the transistors Q, , Qt, whose resistance values rbl and rbg are about 100 to 200Ω, which are so small that they can be ignored at the input section. Also, 17
．． 18 are equal input sources (current values are gm, ・V
in, gmz ・Vjn), 19 is a constant current source 9
The value RUB is very large and its influence can be ignored.

Further, FIG. 11 shows only one side of the equivalent circuit of FIG. 9, and the gain of the differential amplifier circuit will be determined using FIGS. 10 and 11.

First, the mutual conductance gmI is and r131 is given by ni-T It is.

However, k is the Boltzmann constant, q is the amount of electron charge, T is the absolute temperature, and (1) is the collector current of the transistor Q+, so that the gain AV is determined by the equation (3).

Vin Vin Child GM, -RL r81 10R.

[Problem that the invention seeks to solve]

The conventional analysis method for semiconductor integrated circuits is as described above.
The gain was determined using an equivalent circuit for small signals as shown in Figures 0 and 11, but analysis of large signals requires a separate equivalent circuit for large signals, and it is necessary to calculate the gain between the extremes of small and large signals. The gain could only be calculated in certain cases, and its value could only be approximated.

In addition, the operating state centering on the operating point and the formula expressing the gain do not correspond visually, and the gain obtained from the equivalent circuit can only be determined from the values of several points obtained from the equivalent circuit for large signals and small signals. Therefore, there was a drawback that it was difficult to grasp the entire operating state.

This invention was made in order to solve the above-mentioned problems with the conventional ones, and allows settings to be made so that the overall image of nonlinear characteristics corresponds to the gain calculation, so that advanced electronic circuits can be quickly and accurately used. This paper aims to provide a method for analyzing semiconductor integrated circuits that can be designed.

[Means for solving problems]

The analysis method of a semiconductor integrated circuit according to the present invention is as follows: Focusing on the current value flowing through each collector of the input transistor of the differential amplifier circuit, standardizing the change in the value as the modulation degree, and using this modulation degree as the differential This is to find the gain of the amplification circuit.

[Effect]

In this invention, since the degree of modulation indicates the operating state of the differential circuit, the gain from small signals to large signals can be accurately determined.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a differential amplifier circuit analyzed by a semiconductor integrated circuit analysis method according to an embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 9 indicate the same parts.

Now, input terminal T1. The input Vin is applied between Tt, and the collector current of the input transistors Q, , Q, ■1°■! When flowing, ■, dry I0 ・ (1 + α) ... (4
)12-10 ・(l-α)
...(5) then (1), (From formula 21, ■. ...(6)!.

The above α is defined as the modulation degree of the differential amplifier circuit.

The physical meaning of this modulation degree will be explained using FIG. In FIG. 2, when Rr-Rt=0 for convenience of explanation, the horizontal axis shows the input terminal Vin (including positive and negative), and the vertical axis shows the collector current 1. ．． 1. shows. In the figure, however, V is set to -T/q, N>>1, for example, N-10
~20. At this time, the amount of signal current 1 s modulated by the collector currents I, , I□ of transistors Q+ and Qz
As is clear from FIG. 2, tg is expressed by equation (8).

I sig I+ -Xt -21o ・α ・
...(8) Next, based on the physical meaning of the above modulation degree,
Calculate the gain of the circuit shown in Figure 1. In Fig. 1, the input voltage is Vin-Vl -Vz q Iz...(9) However, VBI''VB2.
is the reverse saturation current of transistors Q, , Q2.

The output voltage is expressed as (to).

Vo -RLI' I + -RLz ・I
z=Rt+ (1+ -Iz)
...where RLI-RL□ is α.

Substituting the above equation (41, (5)) into the above equation (9), αφ, Vin=21. ・R, ・α Vo =2RL−To 'α ・a'a
becomes. Here, from the above formulas <8), (11), and 021, they become mutually input, and the gain AV becomes...
Indicates accurate values including nonlinear characteristics. However, formula 00, which corresponds to the denominator of formula Q31,041,
-aJnx+b, which cannot be expressed in the form of a linear equation, so a general solution cannot be obtained.

However, the circuit constants (Rr, Rz, RLI
, RLt) and parameters are set, if you create a program like the one shown in Figure 4 according to the flow shown in Figure 3, you can easily find the optimal solution by numerical calculation using a simple program calculator. This makes it possible to design the gain of any differential circuit.

FIG. 3 shows the input voltage value V in and bias current value ■ of the differential circuit. , resistance value R, and the modulation degree α and gain gm of the differential circuit. In the figure, 31 is the input voltage value Vin and the bias current value ■. .

step of inputting the resistance value R7; 32 is a step of calculating the modulation degree α from the input voltage value V in, bias current value 1o, and resistance value R; 33 is a step of calculating the gain gm of the circuit from the modulation degree α; 34 is a step of outputting the modulation degree α and gain gm.

Also, FIG. 4 shows a program written in a basic language that corresponds to the flow shown in FIG. 31, lines with sentence numbers 50 to 140 correspond to steps 32 to 34 in FIG. Text number 15
The 0 line is the end line.

Here, in order to confirm r11, we will expand the 01.00 formula at the small signal level. When the signal is small, the modulation degree α becomes small (α<<1'), and Equation 03 becomes, which corresponds to Equation (1) above. And the gain A at this time
Assuming that v is Av=gm-R1, an equivalent to equation (3) is obtained.

Next, the characteristic profile of the dynamic range (-1<α<1) of the modulation degree α with respect to the input Vin will be examined using FIG. For this reason, first the Vin-α characteristic curve (fifth
Find the slope of (Fig.).

From the 00 formula, Vin dα...a[9 Here, as a definition of the dynamic range of the input of the differential amplifier, the slope at the origin (Vin=O) in Figure 5 is found, and the modulation degree α-1 (100 %) and α=-1 (-100%). From equation 01, the slope at the origin is as follows, where Vin-D=K・α...(2) holds, so by substituting α-±1 into the equation α, we get the fifth
The Vin-α characteristic curve shown in the figure is drawn, and when α=±1, it is as shown in Table 1.

Table 1 The narrowest dynamic range of the input of the differential amplifier is when R, -Rt -0 (Ω), and the minimum value is α
From the formula η and α1, −T Vtn−D(win) = 2 ・−(19),
Vtn-D (win) ”%51.4 (mV) at room temperature
becomes.

Next, in formula 09, I. -R1>> (k-
T/q) (for example, Io ・R+ #50
If 0~100100O, then Kpζ2■.・R, ... (20) Vinp''q2to -R1-cx -Kp・α ... (21) = R, I
l51g = (22).

As shown in these four equations, the slope of the operating characteristic curve in Figure 5 is the resistance R.
1 and is a straight line (however, IO is a constant current), and the relationship between the input (Vinp) and the modulation degree α is a proportional relationship as shown in equation (21).

Therefore, by setting the conditions so that the above equations (20) and (22) hold, the voltage
The design of a current (V-1) conversion circuit can also be easily implemented using this analysis method (signal component Isig of the collector current of transistors Q, , Q, with respect to the input voltage Vin)
21°・a is used as the output).

Figure 6 shows the operating characteristic curve when a sine wave is actually applied to the input using Figure 5, and the modulation degree of the output current is plotted on the vertical axis. can be visually grasped (in general, the input Vin is an arbitrary function).

What has been explained above will be summarized again and explained along the design procedure (when using basic differential amplifier circuit cells).

1. Decide whether to design it as a voltage amplification circuit or a vr conversion circuit.

2. When designing as a voltage amplification circuit 2-1) Determine the dynamic range (Io) of the output current.

2-2) Determine the dynamic range of the input using the on and am formula, and determine the resistance R+ and Rz values (the mutual conductance gm is also determined at the same time). If necessary, perform numerical calculations using the program shown in Figure 4, etc. .

2-3) Select a load resistance value and determine Ga1n = gm-RL.

3. When designing as a V-1 conversion circuit, 3-1)
■ When linearity is important.・Insert the condition R, >> (k・T)/q.

3-2) Dynamic range of output current (1,')
decide.

3-3) Input current dynamic range o7).

Determine from 0 to formula.

4. *Create an operating characteristic curve as shown in Figure 5 for verification.

4-1) The extension can be obtained from the above formula 09, and the outline of the characteristic curve can be calculated using the ag+ formula.

4-2) Use the program in Figure 4 to input any input V.
The modulation degree α with respect to in is repeatedly calculated and plotted to create FIG.

4-3) However, FIG. 5 is created for confirmation, and can be omitted if the understanding deepens.

5. Application to other circuits In section 4 above, typical voltage amplification circuits, voltage-current (V
-I) Although we have applied and explained the application to conversion circuits, this analysis method can also be applied to any electronic circuits configured based on differential circuits, such as other multiplication circuits and absolute value circuits. It is.

FIG. 7 shows an example of a multiplication circuit analyzed using the analysis method of the present invention, and in the figure, reference numerals 20, 21, 22 and 23 indicate transistors (Q3, , Qs) constituting the multiplication section.

24.25 is the second input terminal (also written as Ts and 'rb).

In FIG. 7, 1. When the second inputs Vα, ■β are applied to the respective input terminals T+, Tz and T, . Qa, Q
Suppose that the currents at the output section of the second circuit section constituted by s and Qb are modulated by a modulation degree α and a modulation degree β, respectively. It is also assumed that the collector sizes of the transistors Q3 and Q4 are set to 1:(N-1), respectively, of the N5 multi-collector transistors Q4 and Qs.

At this time, if the output voltages between the output terminals Ts and T4 and the ground are Vo, Vo, respectively, then the output voltages Vo,
Voz is Vow-[(1+α)・(1+β)+□・(1+α)・(1-β)] x −x 10 ・RLI ・・・(23) VOz
= [(1-α)・(1+β)+□・(1-α)
・(1−β)] ×□×■.・R4,2...(24) At this time, the output voltage 'J between terminals Ts and Ts
O-V O1-V Oz = ((1+β)+ −-(1-β)) ・Io RL
°α・Io ・RL ・α ・10 ・RL ・α ... (25) = (1+β°)・Kla ・RL ・α ...(
26)−(1+β゛)・K −vo−α ・・
・(27) However, RL+”Rtt−RL is −(1+ −−) VO−α−■・RL・α.

In the above equation (25), if N>>1, the following equation is obtained.

VO'#(1+β)・I−Rt・α′q(1+
β)・Vo...(28) This means that in Fig. 7, transistors Qa and Qs do not become multi-collectors; the connection is broken at point 0 (X and Y) in the figure, and transistors Q, , Q4 , Qs, and Qh correspond to a circuit in which identical transistors with the same collector size are connected.

Figure 8 shows transistors Q, , Q in the circuit of Figure 7.
A characteristic diagram is shown when the collector area ratio of , is 1:3, and is set to N-4.

In FIG. 8, the horizontal axis represents the modulation degree β (amplitude modulation is obtained by multiplying the output V by -α), and the vertical axis represents the output voltage V.

The characteristic curve when taking is shown by the line segment a-b, which is (2
It can be seen that this corresponds to equations 5) to (27).

Similarly, it can be seen that the line segment ac (single-dot chain vA) corresponds to the above equation (28).

In this way, by understanding the meaning of the degree of modulation for each characteristic and looking at equations (25) to (27) and FIG. 8, the operating status can be visually understood.

In this way, when a semiconductor integrated circuit is designed using the semiconductor integrated circuit analysis method according to this embodiment, the dynamic range of the input can be theoretically and easily obtained, and the input/output relationship of even a complex and large circuit can be easily determined. Since both formulas and characteristic diagrams can be obtained, it is possible to easily design multiplication circuits, V-1 conversion circuits, etc. based on differential circuits, in addition to differential amplification circuits, and the inventor of the present invention By applying this design method, we were able to design a high-performance IC for analog signal processing that can be applied to television receivers, floppy disk drives, etc. Furthermore, accurate and quick circuit design becomes possible, and design costs can be reduced, resulting in the effect that high-performance ICs can be obtained at low cost.

〔Effect of the invention〕

As described above, according to the method for analyzing a semiconductor integrated circuit according to the present invention, the degree of modulation is the normalized change in the current flowing through each collector of the differential transistor, and the degree of modulation is determined based on the degree of modulation. Since the gain is calculated, there is an effect that the nonlinear characteristics of the differential circuit and the gain calculation correspond to each other.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cell of a differential amplifier circuit analyzed according to an embodiment of the present invention, and FIGS. 2 to 6 illustrate a method for analyzing a semiconductor integrated circuit according to an embodiment of the present invention. Figure 2 is an explanatory characteristic diagram of Figure 1, Figure 3 is a diagram showing the flow for determining the modulation degree and gain, Figure 4 is a diagram showing the program corresponding to Figure 3, and Figure 5 is the diagram of Figure 1. A diagram showing the relationship between input voltage and modulation degree, and FIG. 6 is an explanatory characteristic diagram showing the correspondence between the input and output waveforms in FIG. 1. Further, FIG. 7 is a diagram showing an example of a circuit analyzed by the analysis method according to an embodiment of the present invention, FIG. 8 is a characteristic diagram for explaining FIG. 7, and FIG. 9 is a diagram showing a differential circuit analyzed by the conventional method. Diagrams showing cells of the amplification circuit, Fig. 10, Fig. 1
FIG. 1 is an equivalent circuit diagram used in a conventional analysis method. 5.6...Input transistor, 7.8...Resistor, 1
0.11...Load resistance, 9...Constant current source. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 2 Figure 3 Figure 5 (-) Vin (・) Figure 4 1o: ``GM PROGRAM'''20: I
NPUT VmV” V2O: INPUT
"ImA"140;INPUT"ROH"
M”, R50: M=1・N=-1
60: A = (M-N)/2 70- B = 2 R*ItA Order 25°7*LN ((1◆A)/(1-A)) 80:
IF M-N<10↑-6THEN 1309
0:IF BnV THEN 110100:
GOTO120 110: M=A: GOTO60120:
N=A: GOTO60130・PRI
NT ゛弘＝”;'A140・PRINT ”G
M=; 2*I)+-A/v150・EN
D Figure 6 Figure 7 Figure 9 Figure 10

Claims (2)

[Claims] (1) A method for analyzing a differential amplifier type circuit network of a semiconductor integrated circuit, in which the bias current on the common emitter side of the input transistors of the differential circuit is set to 2I_0, and an input is applied between the base terminals of the input transistors. The amount of change ΔI (=Ic - I_0) in the complementary currents obtained on the collector side of the input transistor when The modulation factor α (-1≦α≦1) is obtained by dividing and normalizing by When it is desired to obtain quantitative data of a differential circuit at the time of design, the data is calculated by numerical calculation based on the above-mentioned relational expression, and the nonlinear characteristics are drawn by plotting the above-mentioned relational expression on the x, y plane. A method for analyzing semiconductor integrated circuits. (2) The method for analyzing a semiconductor integrated circuit according to claim 1, wherein the differential circuit is a differential amplifier or a circuit configured based on a differential amplifier. .