To be able to find, we must find two of the three currents:, and. The current following into the lower 1-k resistor is exactly equal to ; why? The Page. Solution: Figure For Example 2. The logical operation OR is performed by applying consecutively the two arithmetic operations addition and comparison the input resistor network acts as a parallel voltage summer with equally weighted inputs and the following common-emitter transistor stage as a voltage comparator with a threshold about 0.
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To effectively isolate the individual parameters of a BJT, some device measurements require that the collector is biased and the emitter grounded, while some require that the emitter is biased and the collector grounded. These procedures assume that in-fixture measurements are made with the device mounted in the fixture in a common-emitter configuration as shown in the following figure.
In some measurements, the collector is synchronized to the emitter with an offset, to provide data equivalent to that of a common-collector configuration. Note An earlier version of the Agilent A high-frequency BJT model made use of a BJT switching adapter to switch the device between biased-collector and biased-emitter configurations.
Now a synchronized sweep SYNC is used to synchronize the base and collector SMUs together, allowing all measurements to be made using a common-emitter configuration thus eliminating the need for the switching adapter. The procedures in this chapter include detailed instructions for:.
Note Measurement parameters and measured data are specific to individual devices. Information and data are provided here as examples and guidelines, and are not intended to represent the only correct method or results.
They provide guidelines on setting the values to measure your device. However, the values you use will be based on your knowledge of your device and on information provided in its device data sheet, as well as on the guidelines provided here: they may or may not correspond with the examples. In some cases, it may be necessary to set the input values, make a measurement, and then reset the inputs based on the measurement results.
The procedures give suggestions on judging the applicability of the input values and measured data. The illustrations of plotted data are provided as visual examples of possible measurement results. They are not intended to represent a sequential measurement of one device, nor do they necessarily correspond with the example measurement inputs described in the procedures.
The plots can be used to check the reasonableness of your own measured data, which should appear similar in shape but not necessarily coincident in values.
This data is from the measurement of a single device, and shows another example of possible results. Many, though not all, of the input settings for this measurement correspond with the example settings. The DUTs for example DC indicated by the inverted triangles, are groupings of similar measurement setups used to extract related model parameters. The setups contain the information used to define the inputs and outputs for each measurement, as well as their measurement hardware configurations and their associated transforms and plots.
The DC measurement procedures measure DC current or voltage versus bias under different bias conditions. Leave the network analyzer disconnected from the bias networks while you perform the DC measurements, with the RF IN connectors of the bias networks terminated to prevent possible bias oscillation.
For each of the measurement setups, it is necessary to define the instrument states options for the measurement instruments that will be used in that setup. The instrument states need to be defined individually for each setup.
Different setups use different measurement instruments. However, with minor exceptions that will be explained, the instrument states for the same measurement type must be used for all the setups that use that measurement type. To define the instrument state for any given setup:. The instrument state settings will be explained in this chapter with their corresponding setups.
The forward and reverse gummel measurements plot the operating range of the base and collector currents with the transistor in the forward active and reverse active modes. All coefficients of the DC model equations are derived from the fgummel and the rgummel data. This procedure measures Ic and Ib with respect to Vbe. The base and collector are swept across a range large enough that both high-level and low-level effects occur.
This measurement should always be done first because its result is used to properly define the ranges of subsequent measurement setups. Follow the steps described in the appropriate chapter shown next:. Then return to this chapter and continue. This procedure defines the input signals to be applied to the device under test for this measurement.
You provide compliance values to limit SMU output voltage or current and prevent damage to the device under test, as well as to the SMUs, bias networks, and probes, if used. With a voltage input, compliance refers to current. Refer to your device data sheet as needed for specifications and compliances. The setup inputs and outputs are displayed.
Sweep Type LIN, to provide a linear Vbe sweep from start to stop voltage values Start and Stop Voltage values that define the operating range of the device. The Start value should be low enough so that the Ib curve bends up at the low end due to recombination in the base-emitter depletion region. The Stop value should be large enough so that the Ic curve begins to bend over at the high end due to high-level effects.
This holds the emitter at ground potential to prevent reverse leakage from influencing Ib. Ratio 1. This is the type of data to be plotted, M for measured, S for simulated, or B for both. The illustrations of measured data in this chapter were plotted with the outputs set to M: in the extraction section later in the chapter, where the illustrations show both measured and simulated data, the outputs were set to the default, B. Note Remove any high-intensity light sources such as microscope light before taking a measurement.
This is particularly important if currents in the nanoamp range are being measured. One simple method of blocking light is to place an opaque plastic box on the fixture directly above the device. Observe antistatic precautions. Do not touch the fixture or the bias networks while the system is measuring.
If the Ic curve does not bend over at the high end, go back to the inputs and set vb Stop to a larger value. Be careful, however, not to exceed the maximum current rating of the device. If the Ib curve does not bend up at the low end, set vb Start to a smaller value. Repeat the measurement.
The other plots are used later, in the extraction process. The emitter and base are grounded, and the base-collector voltage is swept across a negative range wide enough to show both high-level effects and low-level depletion effects. Use the same settings for the rgummel setup as you did for the fgummel. Note The instrument states need to be set independently for each setup. The Stop value should be large enough that the Ie curve begins to bend over at the high end due to high-level effects.
Synchronization is not necessary for this measurement. The plot will be updated with the measured data. If the Ie curve does not bend over at the high end, go back to the inputs and set vc Stop to a larger value. Making the Forward Early Measurement The forward early measurement models the effect of base-width modulation due to variations in the base-collector depletion region. This procedure measures Ic with respect to Vce at a single value of Vbe.
The emitter is grounded and the collector voltage is swept. The Vbe value is taken from the log-linear region of the fgummel measurement. The data from this measurement will be used to extract VAF, the forward early voltage.
Use the same settings as for the fgummel measurement, except set Integ Time to M medium if you prefer. This should be in the log-linear range of the fgummel measurement, between the high- and low-level effects. To determine the Vb value, refer to the measured data from the fgummel measurement. The rearly measurement uses the sync function, and it can only synchronize on one base value.
Referring to the data sheet for your device, set the Stop value the upper limit of the device's normal operating range. If you are not satisfied with the data, go back to the inputs and change the vb or vc values, staying within the log-linear range of the fgummel measurement for vb. Making the Reverse Early Measurement The reverse early measurement models the effect of base-width modulation due to variations in the base-emitter depletion region.
This procedure measures Ie with respect to - Vce. The base is synchronized to the collector. The Vbc values are taken from the - Vc values in the log-linear region of the rgummel measurement, taking the device from near cutoff to near saturation. The data from this measurement will be used to extract VAR, the reverse early voltage.
Follow the same procedure you used in the fearly measurement. Use the same settings. This should be in the log-linear range of the rgummel measurement, between the high- and low-level effects. The ratio of vb to vc is If you are not satisfied with the measured data, go back to the inputs and change the vc values or the vb offset. The collector is set to the same values as in the fearly measurement, but the base voltage is set for measurements at three values.
This allows you to view the device behavior over a wider range of base input voltages. One of the base voltage values is the same as the value used in the fearly measurement. Set vb Start and Stop to values in the log-linear range of the fgummel measurement, between the high- and low-level effects.
The step size should be sufficient that the resulting measured Ic curves will be clearly separated and easily distinguishable. Making the rcflyback Measurement This procedure drives the base with a current to negate the effect of the base parasitic resistance. The change in negative collector voltage is monitored vs the change in base current.
The collector voltage is the base current times the parasitic resistance in the collector. The data from this measurement is used to extract the parasitic collector resistance RC. This is done with a ratio of - 1 and an offset of 0.
The measured data should be similar to that shown in the following figure. The straight line is measured - Vc data. It should be fairly linear, and should only begin to deviate from a straight line at the high end of the base current value, if at all. If necessary, you can go back to the inputs and change the ib Stop value, then repeat the measurement. Figure 43 Example Measured rcflyback vcvsib Data.
Bjt differential amplifier problems and solutions
To be able to find, we must find two of the three currents:, and. The current following into the lower 1-k resistor is exactly equal to ; why? The Page. Solution: Figure For Example 2. How does a current mirror work? DC modeling lets you determine current-ratio, and thus Iout of the mirroring device.
BJT EXERCISES WITH SOLUTIONS FILETYPE PDF
Instrumentation amplifier: Combines very high input impedance, high common-mode rejection, low DC offset, and other properties used in making very accurate, low-noise measurements Is made by adding a non-inverting buffer to each input of the differential amplifier to increase the input impedance. The resulting voltage can be obtained from the output pin. From the theory of semiconductor physics, There are several methods to design this differential amplifier. The inverting operational amplifier see circuit number 2 amplified a voltage that was applied on the inverting pin, and the output voltage was out of phase. Bipolar Transistor Basics In the.