HG_DS1

AmQRP AmQRP .ORG Paul Harden, NA5N HOMEBREWER The No. 5 2N2222 2N3904 2N4401 MPS2222 MPS3904 The Handyman's Guide to – The Handyman's Guide to – UNDERSTANDING UNDERSTANDING TRANSISTOR TRANSISTOR DATA SHEETS DATA SHEETS & SPECIFICATIONS & SPECIFICATIONS Introduction The most common bipolar junction transistors (BJT) used by hobbyists and QRPers are the 2N2222, 2N3904 and 2N4401. These NPN transistors have similar characteristics, and perform well at HF frequencies. This tutorial explains how to "read" the data sheets on these devices and understand the specifications – which will enable you to interpret data sheets for other devices as well. ____________________ The manufacturer's data sheets contains information in the following general categories: 1. 2. 3. 4. Maximum (Breakdown) Ratings "On" Characteristics Small Signal Characteristics Switching Characteristics er's PFavorite QR GENERAL PURPOSE NPN TRANSISTORS TO–92 Plastic Encapsulated Transistor C B E EB C TO–18 Metal Can Transistor E B C Bottom View C B E SOT-23 Surface Mount Transistor C MMBT2222LT1 MMBT3904LT1 MMBT4401LT1 1. Maximum (Breakdown) Ratings The maximum ratings are provided to ensure that the voltages and currents applied do not damage or cause excessive heating to the device. The maximum ratings for the 2N2222, 2N3904 and 2N4401are shown in Table 1. The voltages, currents and power dissipation listed should not be exceeded to prevent damage to the device. VCEO is the maximum collectoremitter voltage and VCBO is the maximum collector-base voltage. Fortunately, these breakdown voltages are well above the typical 12v used in most QRP applications. This is not the case with VEBO, the maximum emitter-base voltage, typically 5–6v. If exceeded, this can cause a physical breakdown of the base junction, destroying the AmQRP Homebrewer, Issue #5 B E Table 1 – MAXIMUM (BREAKDOWN) RATINGS 2N 2222 Collector–Emitter Collector–Base Emitter–Base Max. Coll. Current Power dissipation 1 VCEO VCBO VEBO Ic Pd 30v 60v 5v 2N 2222A 40v 75v 6v 2N 3904 40v 60v 6v 2N 4401 40v 60v 6v MMBT 3904 40v 60v 6v 600mA 600mA 200mA 600mA 200mA 625mW 625mW 625mW 625mW 225mW © 2005, AmQRP, All rights reserved 50 Statistically. This is why 150 the data sheets list both HFE (min) and HFE (max). . to be safely below VEBO. Ic plot and 10mA. The destruction of a transistor in this manner is technically Table 2 – DC "ON" CHARACTERISTICS called catastrophic substrate failure for good reason! 2N 2N 2N 2N MMBT C 2222 2222A 35 50 150 75 250 3904 40 70 200 100 300 4401 20 40 — 80 — 3904 40 70 200 100 300 0. Conventions used in electronic literature: This is why the data is listed with the test conditions. However. VBE. It is used for biasing the device in is the AC current gain the linear region – primarily class A. 2N2222 C DC Current Gain. ON CHARACTERISTICS Collector-Emitter Saturation Voltage. VCE(sat) Ic= 150mA. the biasing scheme sets the baseemitter voltage.Handyman's Guide to . is the other maximum rating to be closely followed." The DC Characteristics in Table 2 are not absolute design values. Ic(max). VBE must include the DC base bias and the peak voltage of the signal to ensure VEBO will not be exceeded.0 mA. The 100 manufacturer tested a large batch of 2N2222s and ) (min 70 determined that hfe ranged from 50 (HFE min) to 150 (HFE HFE 1 HFE (typ) max) at Ic=1mA. and some oscillator circuits. VCE=10v HFE Min. IB= 15mA VBE(sat) 1. HFE HFE min.2 0. or about HFE=100. . All rights reserved X ! X 10 X X X ! X ! . Most data sheets provide HFE at two different collector currents.95vdc . Since most QRP circuits are biased for Ic <5mA = HFE values from data sheet (to conserve battery drain). 1 – Constructing an HFE vs.2vdc† Most QRP circuits are usually biased for well below Ic(max). m ax ) 2 HFE ( 200 3 HFE also varies from transistor–to–transistor. causing collector current † Ic=50mA. Ic=1. PA stages. the collector-emitter junction. usually 1 Fig. and max.85vdc 0.85vdc† while it is forward biased (Vbe >0. initiating thermal runaway – destroying for a transistor is to consult the data sheets. such as RF drivers.4vdc 0. Ic (mA) © 2005. at Ic=1 and 10mA.1 0. Collector current exceeding Ic(max) Rule of thumb for Ic(max): There isn't one! can damage the transistor. IB=5mA on 2N3904 to flow. Vbe(max) and Ic(max) are generally a concern only in largesignal applications. The average AmQRP Homebrewer. HFE Min. or "on. HFE Max. Since the 2N3904 has a higher DC current 20 gain. often HFE=150 is recommended for that device. EBO EBO NA5N Rule of V (max) C Vbe(max)thumb for V :purpose BJTs or for most general is 5–6v – the maximum emitter-base voltage. AmQRP. Issue #5 2 0. IB= 15mA VCE(sat) 0. in large-signal applications. 35 50 150 75 225 2.3 0. HFE Ic= 0. HFE at Ic=1mA is typically 300 used.1mA.3vdc 1.2vdc 0.5 1 2 3 5 Collector Current." HFE or hFE (upper case letters) is the DC Current Gain HFE is the measured DC current gain of the transistor (see Hfe or hfe (lower case) Rule of thumb for HFE).4vdc These specifications define the Base-Emitter Saturation Voltage. most transistors will fall between 50 and 150.3vdc† 0. Rule of thumb for HFE: but rather test values as measured by the manufacturer. Don't forget to include the peak voltage of the AC signal! Collector Current. DC Current Gain. 1). UNDERSTANDING TRANSISTOR DATA SHEETS transistor. In a circuit.3vdc 0. such as "Ic=1mA. VBE(sat) DC performance of the device Ic= 150mA. VCE=10v Ic= 10 mA. VCE=10v HFE Min. can be plotted on a logarithmic graph (lines 1 and 2 on Fig. VCE=10v. due to excessive current The only safe way to know the maximum Ic through the device. as shown on the data sheets (Table 2). HFE Max. This is why most design guides will 30 recommend using a value of HFE=100 for bias calculations.7v). 5 . The data sheets must be used. that is. hfe. Fig. Ic=1. will work 99% of the time. (Cibo and Cobo) Small Signal Current Gain.Handyman's Guide to . defines the transistor behavior outside the linear operating region. are shown in Table 3 50 300 150 75 375 50 300 150 75 375 100 400 200 — — 40 500 225 — — 100 400 200 — — Table 4 – Calculating Ft from Gpe x= Gp(dB) 10 H FE =5 0 10 E= F 0 Gp(mag) = 10 x Gain Bandwidth Product. 3 (next page). HFE Max. forming the +12v transmit voltage on key–down. Ib (uA) 100 H 3. the most important to understand.5mA @ HFE=50 The small signal characteristics include: At Ib=10uA. That is. . On RF transistor data sheets. VCE(sat) and VBE(sat). SMALL SIGNAL CHARACTERISTICS The small-signal characteristics describe the AC performance of the device. The value used for HFE is not critical. Gp (or Gpe for common emitter power gain) is tested at a specific frequency. All rights reserved . one scarcely needs the data sheets for the DC characteristics.5 = 32 Ft = 200MHz 32 = 1130 MHz © 2005. is defined as the frequency at which the AC current gain. equals 1 (0dB). in dB. can then be drawn (line 3. Ib defines HFE 10 5 3 2 1 . Determine Ft. Ft (MHz). Issue #5 3 Ft = f Gp(mag) Example: The data sheet for the 2N5179 lists Gpe=15dB at 200MHz.0mA @ HFE=100 1) gain bandwidth product (Ft) Table 3 – SMALL SIGNAL CHARACTERISTICS – Part 1 2) the AC current gain (hfe) 2N 2N 2N 2N MMBT 3) input and output impedances 2222 2222A 3904 4401 3904 (hie and hoe) 250 300 300 250 300 4) input and output capacitances Gain Bandwidth Prod.. in the saturated region. There is no standardized industry definition of smallsignal (vs. . Instead.1 1 10 3 5 30 50 Base Current. to unitless magnitude. hfe 5) the noise figure (NF). or Ft. and used in the † Measured at 1 KHz circuit design equations. The small-signal characteristics for Ft and hfe.5 10 Gp(mag)= 10 1. NA5N C Rule tof thumbrfor HFE:p o s e Mos gene al pur NPN transistors have a DC HFE = 100 (typ) and thus used in most biasing equations for DC and low frequencies. UNDERSTANDING TRANSISTOR DATA SHEETS value. At Ib=10uA. HFE typ. AmQRP. 2 shows Ib vs. as the typical HFE = 100 at Ic=1mA is valid for most general purpose NPN transistors. Collector Current. See Fig. or even the conservative value of 50.3 . transistor's behavior at audio and RF frequencies. Ic=1. is an example of a saturated switch. The keying transistor in a transmitter. Ic (mA) Saturation voltages.2 . This is of interest when operating the transistor as a saturated switch. This is the maximum frequency the device produces gain as an amplifier or oscillator. Equations x and Gp(mag) convert the power gain. Ft can be derived from this information as shown in Table 4. Vce=10v† hfe Min. hfe Max. the signal levels are well within the linear operating region of the transistor. as is hfe. This gives you HFE (typ) for various collector currents. Ic=0. Therefore. 1). Ic for HFE at 50 and 100. but is generally defined where the AC signal is small compared to the DC bias voltage.0 mA. large-signal). Fig. Using HFE=100. the power gain. 2 – Ic vs. Ft is not always given. The small signal parameters are Estimated hfe Typ. Vce=10v† HFE Min. Fig. AmQRP Homebrewer. from the data sheets. as they describe the Ic= 10 mA. such that making assumptions (as we did with DC HFE =~100) can be risky. x= 15dB = 1. These parameters vary greatly from one transistor type to another. where hfe is measured. or fb=Ft/hfeo. fo.3 0. Design Example: Constructing an Hfe vs. hfe=50 (min) to 300 (max). Collector Current 300 200 150 100 70 50 30 0. Frequency hfe hfeo hfeo=hfe @ 1KHz –3dB slope = 6dB per octave Ft. calculate hfe at the desired frequency. Ic. Firstly. The values for hfe shown in the data sheets are normally measured at 1KHz and Ic=1mA (sometimes @10mA). Let's pick hfe=150 as the average. or almost unity! This is why general purpose transistors (Ft <400MHz) are not used at VHF for lack of useful gain above ~50 MHz. 5 – Hfe vs. where hfe= 0. is the "3db point" of hfe. since most parameters are listed for Ic=1mA. are seldom shown in the data books. . Ft and hfe work together to define the overall AC gain of the transistor at a specific frequency. MHz 100 1000 7 MHz Ft=250 MHz For gain at any frequency.707 x 150 = 106 Draw a dot at hfe@fb on the chart (hfe=106 @ 1. For designing battery powered circuits. Fig.Handyman's Guide to . fb. Fb is seldom listed on the data sheets. This is why learning to interpret the data sheets is important to determine the actual gain (hfe) a transistor will provide at a specific frequency.707hfeo = 0.7. fb < fo < Ft Ft Gain(dB) = 10log(hfe) hfe = fo Fig.1 1 2 3 1 2N4401 2 2N3904 3 2N2222 10 0. Calculate fb and hfe @fb as follows: (Ft=250MHz. It's really easy. hfe drops fairly linearly from fb to Ft at 6dB/octave. Draw a line on a chart to represent hfeo=150 (line #1. Hfe is also known as the ac beta.707 hfeo hfe=1 1KHz fb f Fig. these transistors have ample gains at Ic=1mA or less. 2N2222) fb = Ft/hfeo = 250MHz ¸ 150 = 1.7 MHz 10 hfe=36 @ 5 MHz 1 ! 36 3 2N2222A 1 Ic = 1mA 0. All rights reserved .707hfeo. The additional gain at a higher Ic may not justify AmQRP Homebrewer. Frequency Plot Let's figure out what hfe will be for a 2N2222 on the 40M band. hfe How much signal gain will the 2N2222 provide at 144 MHz? hfe = Ft/fo = 250MHz ¸ 144MHz = 1. using both graphical and equational methods. where hfe=1 Ft fb.5 1 3 5 Collector Current. Since hfe is measured at 1KHz.7 MHz hfe@fb = . where hfe=.1 1 10 Frequency.) 300 2 ! AC Current Gain. Hfe is also a function of Ic as shown in Fig. at 7 MHz ac gain is hfe = 36 AC Current Gain. Therefore. AmQRP. as illustrated in Fig. data sheet values can be used directly. Fig. such as 7MHz hfe@fo = Ft/fo = 250MHz ¸ 7MHz = 36 Draw a line between fb (or fo) and Ft (line #2. this is also hfeo. and the hfe vs.. 3 – Common Emitter AC current gain vs. often very close to the DC HFE. Hfe vs. 5. frequency plots. Hfeo is fairly constant from the audio frequencies to about 300 KHz. and dependent on both frequency and the collector current. Fb. UNDERSTANDING TRANSISTOR DATA SHEETS hfe is the ac small-signal current gain. Issue #5 4 NA5N Fig. hfe 100 hfe=106 30 @ 1. frequency plot of the 2N2222 at Ic=1mA. This data sheet chart is used to adjust hfe at Ic other than 1mA. 3. 4) to complete the hfe vs. 4 – Constructing an hfe gain plot for the 2N2222 (Common Emitter) hfeo=150 (audio freq. Beta cut-off frequency. .7 MHz) Or . Ic=1mA is recommended. saving additional calculations. From Table 3. 4).. Ic © 2005. Secondly. hfeo is the low-frequency hfe. at hoe(typ)=10umhos. the input impedance is called Zin. or Ro = Rc||hoe. All rights reserved . The differences between the two methods. UNDERSTANDING TRANSISTOR DATA SHEETS the increase in battery drain. hoe. Rin. is the capacitance across the baseemitter junction. AmQRP Homebrewer. Rc. As a result.† hie (min) hie (max) Output Admittance † hoe (min) hoe (max) NF (max) Input impedance. for the common-emitter transistor. Ro. Rin Rb Re CE Rin = re(hfe+1) re = 26 Ie(mA) © 2005. . AmQRP. Since Rc tends to be in the 1–5KW range. Rout = 1/hoe = 1/10umhos = 100KW. typ. the better.0 21.0 28. See Fig. For example. In this case. and hoe 20–100KW. as follows: Rin = re(hfe+1) where. is approximately the parallel equivalent of hoe and the collector load resistance. not hie. . As can be seen.0 10.0 50. Note that the output impedance is set primarily by circuit values (Rc). Cibo(max)=30pF. Xc(Cibo) dictates the input impedance of the transistor. output impedance is usually estimated by: Zo » Rc.Noise Figure † emitter junction. while close. Like hie. ‡ Measured at 1 MHz * mmhos Table 6 – 2N2222 Input Impedances based on hfeo=150 Freq hfe based on hfe and re Rin based on Xc(Cibo) || hie Xc(Cibo) Zin Input capacitance. two amplifiers at Ic=1mA will yield far more gain than one amplifier at Ic=2mA. 6. In this case. hie. Output Resistance.1 14. Rc will dominate the output resistance of the transistor.5dB NA5N MMBT 3904 8pF 4pF 1KW 10KW 1* 40* 4dB Input Impedance. demonstrates the difficulty in determining with certainty the input impedance of a transistor. Input resistance. represents the output resistance of the transistor by taking the reciprocal of the admittance. Cibo. I. Cibo = 30pF hie = 5KW Fig. This method is generally preferred since hfe and Ie are known with greater accuracy than is hie and Cibo. The reactance (Xc) of Cibo is in parallel with hie (Xc||hie) – causing the equivalent input impedance.. can also be estimated using hfe and emitter current. Issue #5 5 Rin=re(hfe+1) where. is the resistive element of the base. Table 6 shows hfe at different frequencies for the 2N2222. Table 5 – SMALL SIGNAL CHARACTERISTICS – Part 2 2N 2222 Input capacitance ‡ Output capacitance‡ Cibo (max) Cobo (max) 30pF 8pF 2KW 8KW 5* 35* 4dB 2N 2222A 25pF 8pF 2KW 8KW 5* 35* 4dB 2N 3904 8pF 4pF 1KW 10KW 1* 40* 5dB 2N 4401 30pF 7pF 1KW 15KW 1* 30* 4. since it includes the frequency dependent reactance components. to be frequency dependent as shown in Table 6. hoe is not particularly useful by itself. the smaller the value of Cibo. Cibo is thus important in estimating Zin at any given frequency. re=26/Ie(mA) =26W@1mA Zin(eq) = Xc||hie where.e. For the 2N2222. the input impedance is called Rin. Zin. re = 26 ¸ Ie(mA) (Ie » Ic) 3. Table 5 lists the remaining smallsignal characteristics. and not by the transistor's small-signal parameters. and not particularly useful in itself without considering Cibo. 6 – Input/Output Impedances basic amplifier configuration +12V Ro = Rc•hoe Rc+hoe » Rc Ra Cc Ein Rc Cc Zo. Ro Eout Q1 2N2222 Zin.0 144 71 36 25 18 12 9 5 2 1872W 962W 676W 494W 312W 234W 130W 52W 1516W 758W 525W 379W 253W 190W 106W 37W 1150W 658W 475W 352W 241W 183W 104W 36W The results of Rin from the above are also shown in Table 6 for comparison. since it only includes resistive components (no reactance components). In selecting a transistor for RF. and varies with † Measured at 1 KHz Ic. Output Admittance. It is used for input impedance calculations.Handyman's Guide to .5 7. Ie. far exceeding the 10-12dB NF of a typical HF receiver. UNDERSTANDING TRANSISTOR DATA SHEETS Cobo is the output capacitance. See Table 7. These are really large-signal characteristics. It is presented here for completeness only. the lower the value of Cobo. Noise Figure. or switching applications. SWITCHING CHARACTERISTICS The Switching Characteristics define the operating limits of the transistor when used in pulsed. tr. making the overall system noise a function of the receiver. storage time is the time from the input H–L transition until the output responds. This is usually the longest delay. or the abbreviated listings. tf. a NF of 4-6dB per transistor is sufficient. is another parameter provided on some data sheets. The transistor will add noise. the better. At VHF/UHF – antenna and atmospheric noise is very low. Fig. more noise is introduced to the receiver by the antenna and band conditions than the NF of the stages can introduce. forming signal plus noise output. This parameter is important in RF transistors operating in the VHF/UHF spectrum. often less than 10dB of noise power. gm can be estimated by: gm = . and is in parallel with the output resistance. Issue #5 6 © 2005.Handyman's Guide to . or S+N. the NF of the transistors becomes very important. These switching times. delay time is the time from the input L–H transition until the output begins to respond. fall time is the time it takes the output to go from 90% to 10% output voltage. 7 – Switching Characteristics tr HI tf INPUT LO 90% OUTPUT 10% td ts This tutorial should allow one to interpret the transistor data sheets. or identifying those "ham fest special" transistors and their suitability for your next project. such as found in the NTE Cross-Reference or in the ARRL Handbook. If not provided. gm.038 x Ie(mA). Many manufacturer's provide complete data sheets online. QRP switching circuits include T-R switching. rise time is the time it takes the output to go from 10% to 90% output voltage. and seldom a design criteria when selecting a transistor. . digital logic. however. Table 8 – SWITCHING CHARACTERISTICS 2N 2222 Delay time Rise time Storage time Fall time td tr ts tf 10ns 25ns 225ns 60ns 2N 2222A 10ns 25ns 225ns 60ns 2N 3904 35ns 35ns 200ns 50ns 2N 4401 15ns 20ns 225ns 30ns MMBT 3904 35ns 35ns 200ns 50ns Fig. AmQRP Homebrewer. For HF receiver applications. then be amplified by the hfe of the device just as the signal is. Transconductance. Cobo is <10pF in most general purpose NPN transistors and has little effect at HF. 7 illustrates the switching characteristics terms: td. In other words. neither of which is easily measurable by the amateur. NA5N Table 7 – HF vs VHF Noise Figures At HF – antenna and atmospheric noise is in the 20–30dB range. and the NF of the individual stages. are thousands of times faster than the requirements for QRP applications. where the shunting effect becomes a significant component of the output impedance. The excess in the S+N to signal power is due to the noise figure (NF) of the device. ts. All rights reserved . Obviously. . as this is where it will be the most evident. the NF of the transistor is not highly important on HF. since the transistor is being driven from cut-off to saturation in most switching applications. Select a transistor with a low NF for the audio stage(s). NF. AmQRP. However.5dB to 2dB range not uncommon. Understanding transistor specifications is essential in designing your own circuits. At VHF/UHF. 4. is defined as the ratio of the input to the output noise. whether the complete data sheets from the manufacturer. Biasing transistors using these specs will be presented in a future Handyman's tutorial. in the tens of nanoseconds. For the QRPer. with transistors being selected with NF's in the 1. CW keying and band switching circuits using transistors. This is not the case at VHF.