Philips Semiconductors Letter Symbols - Transistors LETTER SYMBOLS The letter symbols for transistors detailed in this section are based on IEC publication number 148. General • Average total values, e.g. IB(AV) • Peak total values, e.g. IBM • Root-mean-square total values, e.g. IB(RMS). Letter symbols for currents, voltages and powers Lower-case subscripts are used for the indication of values applying to the varying component alone: BASIC LETTERS • Instantaneous values, e.g. ib I, i • Root-mean-square values, e.g. Ib(rms) current V, v voltage • Peak values, e.g. Ibm P, p power. • Average values, e.g. Ib(av). Upper-case letter symbols are used to represent all values except instantaneous values that vary with time, these are represented by lower-case letters. 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 SUBSCRIPTS Transistor currents 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 Transistor voltages 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 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. (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 1999 May 07 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. 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. 126 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 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: Figure 1 represents a transistor collector current as a function of time. It comprises a continuous (DC) current and a varying component. • 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 MBD537 collector current General subscripts The following list comprises the most important general subscripts used for electrical parameters of semiconductor devices. I cm I c(rms) I c(av) ic I CM I C(RMS) I C(AV) IC (no signal) ic 0 time Fig.1 Collector current as a function of time. 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. 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 1999 May 07 Examples: hFE static value of forward current transfer ratio in common-emitter configuration (DC current gain) RE DC value of the external emitter resistance. 127 Philips Semiconductors 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 = Re + jXe small-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 = Ri + jXi, yfe = gfe + jbfe. 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. 1999 May 07 128