Transistors General - Philips Semiconductors / NXP Semiconductors

1999 May 07 126

Philips Semiconductors

Letter Symbols - Transistors General

LETTER SYMBOLS

The letter symbols for transistors detailed in this section

are based on IEC publication number 148.

Letter symbols for currents, voltages and powers

BASIC LETTERS

I, i current

V, v voltage

P, p power.

Upper-case letter symbols are used to represent all values

except instantaneous values that vary with time, these are

represented by lower-case letters.

SUBSCRIPTS

A, a anode terminal

(AV), (av) average value

B, b base terminal

C, c collector terminal

D, d drain terminal

E, e emitter terminal

F, f forward

G, g gate terminal

K, k cathode terminal

M, m peak value

O, o as third subscript: the terminal not

mentioned is open-circuit

R, r as ﬁrst subscript: reverse. As second

subscript: repetitive. As third subscript: with

a speciﬁed resistance between the terminal

not mentioned and the reference terminal

(RMS), (rms) root-mean-square value

S, s as first or second subscript: source terminal

(FETs only). As second subscript:

non-repetitive (not FETs). As third subscript:

short circuit between the terminal not

mentioned and the reference terminal

X, x speciﬁed circuit

Z, z replaces R to indicate the actual working

voltage, current or power of voltage

reference and voltage reference diodes.

No additional subscript is used for DC values.

Upper-case subscripts are used for the indication of:

•Continuous (DC) values (without signal), e.g. IB

•Instantaneous total values, e.g. iB

•Average total values, e.g. IB(AV)

•Peak total values, e.g. IBM

•Root-mean-square total values, e.g. IB(RMS).

Lower-case subscripts are used for the indication of values

applying to the varying component alone:

•Instantaneous values, e.g. ib

•Root-mean-square values, e.g. Ib(rms)

•Peak values, e.g. Ibm

•Average values, e.g. Ib(av).

If more than one subscript is used, the subscript for which

both styles exist are either all upper-case or all lower-case.

ADDITIONAL RULES FOR SUBSCRIPTS

Transistor currents

If it is necessary to indicate the terminal carrying the

current, this should be done by the first subscript

(conventional current flow from the external circuit into the

terminal is positive).

Examples: IB, iB, ib, Ibm.

Transistor voltages

If it is necessary to indicate the points between which a

voltage is measured, this should be done by the first two

subscripts. The first subscript indicates the terminal at

which the voltage is measured and the second the

reference terminal or the circuit node. Where there is no

possibility of confusion, the second subscript may be

omitted.

Examples: VBE, vBE, vbe, Vbem.

Supply voltages or currents

Supply voltages or supply currents are indicated by

repeating the appropriate terminal subscript.

Examples: VCC, IEE.

If it is necessary to indicate a reference terminal, this

should be done by a third subscript.

Example: VCCE.

Subscripts for devices with more than one terminal of the

same kind

If a device has more than one terminal of the same kind,

the subscript is formed by the appropriate letter for the

terminal, followed by a number. In the case of multiple

subscripts, hyphens may be necessary to avoid confusion.

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Philips Semiconductors

Letter Symbols - Transistors General

Examples:

IB2 continuous (DC) current ﬂowing into the second

base terminal

VB2-E continuous (DC) voltage between the terminals of

second base and emitter terminals.

Subscripts for multiple devices

For multiple unit devices, the subscripts are modified by a

number preceding the letter subscript. In the case of

multiple subscripts, hyphens may be necessary to avoid

confusion.

Examples:

I2C continuous (DC) current ﬂowing into the collector

terminal of the second unit

V1C-2C continuous (DC) voltage between the collector

terminals of the ﬁrst and second units.

Application of the rules

Figure 1 represents a transistor collector current as a

function of time. It comprises a continuous (DC) current

and a varying component.

Letter symbols for electrical parameters

DEFINITION

For the purpose of this publication, the term ‘electrical

parameter’ applies to four-pole matrix parameters,

elements of electrical equivalent circuits, electrical

Fig.1 Collector current as a function of time.

MBD537

collector

current

(no signal)

IC(RMS)

Ic(av)

ICM

Ic(rms)

Icm

IC(AV)

time

impedances and admittances, inductances and

capacitances.

BASIC LETTERS

The following list comprises the most important basic

letters used for electrical parameters of semiconductor

devices.

B, b susceptance (imaginary part of an admittance)

C capacitance

G, g conductance (real part of an admittance)

H, h hybrid parameter

L inductance

R, r resistance (real part of an impedance)

X, x reactance (imaginary part of an impedance)

Y, y admittance

Z, z impedance.

Upper-case letters are used for the representation of:

•Electrical parameters of external circuits and of circuits

in which the device forms only a part

•All inductances and capacitances.

Lower-case letters are used for the representation of

electrical parameters inherent in the device, with the

exception of inductances and capacitances.

SUBSCRIPTS

General subscripts

The following list comprises the most important general

subscripts used for electrical parameters of semiconductor

devices.

F, f forward (forward transfer)

I, i (or 1) input

L, l load

O, o (or 2) output

R, r reverse (reverse transfer)

S, s source.

Examples: Zs, hf, hF.

The upper-case variant of a subscript is used for the

designation of static (DC) values.

Examples:

hFE static value of forward current transfer ratio in

common-emitter configuration (DC current gain)

REDC value of the external emitter resistance.

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Letter Symbols - Transistors General

The static value is the slope of the line from the origin to

the operating point on the appropriate characteristic curve,

i.e. the quotient of the appropriate electrical quantities at

the operating point.

The lower-case variant of a subscript is used for the

designation of small-signal values.

Examples:

hfe small-signal value of the short-circuit

forward current transfer ratio in

common-emitter configuration

Ze=R

e+jX

esmall-signal value of the external

impedance.

If more than one subscript is used, subscripts for which

both styles exist are either all upper-case or all lower-case.

Examples: hFE, yRE, hfe.

Subscripts for four-pole matrix parameters

The first letter subscript (or double numeric subscript)

indicates input, output, forward transfer or reverse

transfer.

Examples: hi (or h11), ho (or h22), hf (or h21), hr (or h12).

A further subscript is used for the identification of the circuit

configuration. When no confusion is possible, this further

subscript may be omitted.

Examples: hfe (or h21e), hFE (or h21E).

DISTINCTION BETWEEN REAL AND IMAGINARY PARTS

If it is necessary to distinguish between real and imaginary

parts of electrical parameters, no additional subscripts

should be used. If basic symbols for the real and imaginary

parts exist, these may be used.

Examples: Zi=R

i+jX

fe =g

fe +jb

fe.

If such symbols do not exist, or if they are not suitable, the

following notation is used:

Examples:

Re (hib) etc. for the real part of hib

Im (hib) etc. for the imaginary part of hib.