Presuming you need high frequency oscillators, in the RF Colpitts, Hartley, … oscillators or microwave ranges, you need to chose transistors according to the following guidelines:. Another general consideration when choosing transistors for high frequency oscillators is selecting low noise devices and loading them in the input port, generally such that an enough low noise figure is achieved design for optimum noise. Finally, there are several good books on high frequency oscillator design, such as Andrei Grebennikov: Amazon. I'd have to answer that with a question.
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Jurgen Klinsmann Azevedo Nogueira flag Denunciar. Data sheet. Courtesy Motorola Semiconductor Products Inc. Courtesy Motoroh Semiconductor Products lnc. Courtesy Motorola Semiconductor Products Znc. Equivalent circuit for a 2N at MHz. It is assumed that you are already familiar with the low-frequency portion of the data sheet. Therefore, we will concern ourselves only with that information that is typically added specifically for rf transistors. This particular transistor was chosen simply because the data sheet provides both Y and S parameters and is, therefore, very good for instructional use.
One of the first things you might notice about this particular transistor is that it has four leads! The extra lead is not connected internally to the device itself, but is connected to the case which just happens to be a metal can.
In normal circuit operation, the extra pin is grounded, thus providing a shield around the de- vice to help reduce unwanted stray fields. The first page of the data sheet is fairly straightfor- ward and provides the never-exceed ratings for the transistor. This is a common practice even for low- frequency transistors and is nothing new. Notice that this manufacturer does list those applications in which he feels the transistor might be useful.
This particular device was designed for high-gain, low- noise amplifier, oscillator, and mixer applications. On page 2 of the data sheet, under the heading Dynamic Characteristics, several parameters of inter- est to the rf designer are listed. Keep in mind that fT is only an indication of the frequency at which the current gain of the device drops to 0 dB. Power gain m y still be possible depending upon the available voltage gain from the device at the frequency in ques- tion.
Usually fT is not measured directly for very high- frequency transistors, but is usually extrapolated from data taken at lower frequencies. The accuracy of the measurement is, therefore, somewhat questionable and, as one manufacturer has stated, fT is provided on the data sheets simply for historical reasons. C,,-This is the collector-to-base capacitance of the transistor as measured at 1 MHz with a collector- to-base voltage of 10 volts and the emitter open- circuited.
The smaller this capacitance is, the better off you will be, if you are using the transistor in an amplifier configuration. This capacitance can be equated to C, in the transistor equivalent circuit of Fig. For an rf circuit design, hf, will not do you much good either. The dc beta of the transistor hFE , how- ever, will provide you with needed information in controlling the dc collector or bias current.
This param- eter is listed under the On Characteristics heading for the device on the second page. The smaller this number is, the better off you will be. This is another bit of information that is often ignored. NF-The noise figure of the transistor is simply a mea- sure of how much noise the transistor adds to the signal during the amplification process see Appendix B.
Notice that for these data sheets, a maximum noise figure of 4. This method of presenting the N F for a transistor, as you can well imagine, is practically useless.
Very rarely will the circuit designer ever see the transistor under this exact set of operat- ing conditions. Any variation from these conditions changes the measured noise figure drastically. For this reason, the manufacturer often provides a few noise figure contours which present N F graphically under a wide variety of operating conditions.
2N5179 Datasheet PDF
Sourced from Process The factory should be consulted on applications involving pulsed or low duty cycle operations. NOTE 1: 2 turns No. Learn more about Scribd Membership Home. Much more than documents. Discover everything Scribd has to offer, including books and audiobooks from major publishers. Start Free Trial Cancel anytime.
RF Circuit Design
Jurgen Klinsmann Azevedo Nogueira flag Denunciar. Figure 3 is a graph of noise figure versus fre- quency. The NF is measured at various frequencies under the same Mas conditions. Notice, however, that this measurement was taken with a variable source resistance, where Rs was made equal to its optimum value for a minimum noise figure.
2N5179 TRANSISTOR. Datasheet pdf. Equivalent