 Ft fmax simulation dating, fmax definition

The ft and fmax figures of merit are also calculated and plotted. In this example, the collector voltage is fixed at 2 volts, while the base voltage is swept from 0. A magnitude of 1 is equivalent to zero dB. The frequency at which the power gain is reduced to 0dB is the maximum oscillation frequency or fmax for this specific DC bias point.

Bipolar AC Measurement with ft and fmax Requires: We can make use of the special ft function to extract fmax as well by remembering the following.

In addition, Utmost IV also provides useful shortcuts for specifying the magnitude, phase, real and imaginary parts of these complex numbers. For all AC measurements, the frequencies at which the s-parameters will be measured are defined by the first sweep in the measurement setup. The measurement setup also defines one or more DC bias points at which the frequency dependent s-parameters will be measured. You must also define the DC instrument source connections. These four plots show how the transistor small signal forward current and power gain vary with frequency and DC bias conditions. The power gain of this two port system is best described using Mason's invarient unilateral power gain, U. The exact frequency and bias range you need to use will be determined by the device being measured and also by the limitations of your test equipment.

Unity Gain Bandwidth, ft The unity gain bandwidth ft is defined as the frequency at which the forward small signal current gain hfe of the transistor has a magnitude of 1. During the AC measurement, the s-parameters or scatter parameters will be measured between these two ports.

The emitter of the transistor is connected to the common ground of the two ports.

Once you have the s-parameters of your two port system, you can convert these into other more useful forms, such as impedances, admittances and gains.

At low frequency the gain of the bipolar transistor is relatively constant. For a two port measurement, there will be four s-parameters which are commonly known as s11, s12, s21 and s R This example describes how to perform a bipolar AC measurement and then plot the ft and fmax characteristics.

The emitter is connected to the AC ground of the network analyzer.

The analyzer has two ports which are connected to the bipolar transistor. These s-parameters are complex values, having both real and imaginary parts. All of these impedances, admittances and gains are also complex values. Port 1 is connected to the base and port 2 is connected to the collector.

Acq_ex14 : Bipolar AC Measurement with ft and fmax

Once you reach a certain frequency, the gain will reduce with a single pole roll off. This will allow us to view the typical characteristics which will be generated when the measurement is performed. Maximum Oscillation Frequency, fmax This is defined as the frequency at which the forward small signal power gain of the transistor has a magnitude of 1.

In this case, we set the connection for this terminal to 'manual ground'. AC measurements are typically performed using a network analyzer which measures s-parameters at multiple frequencies. This is all automatically done for you by Utmost IV. 