Changes

===Impedance===

===Impedance===

Next to the output terminal on the signal generator, it says “50Ω.” This means that the output impedance of the signal generator is 50Ω, which is considered a low output impedance. Impedance is similar in concept to resistance, but it includes additional complex elements that describe frequency-dependent resistance in AC circuits. A low impedance output offers a couple of options: you can design the input of your circuit for impedance matching (maximum power transfer to the load) or impedance bridging (maximum voltage signal to the load). In this case, impedance matching would mean that the input impedance of your circuit is also at 50Ω. For impedance bridging, the input impedance of your circuit would be much much greater than 50Ω (on the order of kΩ or MΩ). The circuit you’ll be testing in this certification is designed for impedance bridging with the signal generator.

Next to the output terminal on the signal generator, it says “50Ω.” This means that the output impedance of the signal generator is 50Ω, which is considered a low output impedance. Impedance is similar in concept to resistance, but it includes additional complex elements that describe a frequency-dependent resistance in AC circuits. A low impedance output offers a couple of options: you can design the input of your circuit for impedance matching (maximum power transfer to the load) or impedance bridging (maximum voltage signal to the load). In this case, impedance matching would mean that the input impedance of your circuit is also at 50Ω. For impedance bridging, the input impedance of your circuit would be much much greater than 50Ω (on the order of kΩ or MΩ). The circuit you’ll be testing in this certification is designed for impedance bridging with the signal generator.

Why mention all this business about impedance? This will help you know what to expect from the signal generator and how to design circuits better. In the manual, it states, “Remember that the output signal swing of the generator is limited to ±10V open circuited or ±5V into 50Ω, and applies to the combined peak-to-peak signal and DC offset. Clipping occurs slightly above these levels.” This means that if the signal generator is impedance bridged with your circuit, don’t expect to generate signals outside of a ±10V range. If the signal generator is impedance matched with your circuit, don’t expect to generate signals outside of a ±5V range. This includes the DC offset in both cases. If your input impedance falls anywhere between 50 Ω and an open circuit (∞Ω), the maximum signal you can get from the signal generator will fall between ±5V and ±10V, respectively. Unless you really know what you are doing, do not use the signal generator on circuits that have an input impedance of less than 50 Ω. Similarly, do not choose an injection point in your circuit for the signal generator that has a DC voltage higher than what can be achieved with the DC offset knob. Only choose injection points where the DC voltage can be matched with the DC offset knob; otherwise, this can cause internal damage to the signal generator.

Why mention all this business about impedance? This will help you know what to expect from the signal generator and how to design circuits better. In the manual, it states, “Remember that the output signal swing of the generator is limited to ±10V open circuited or ±5V into 50Ω, and applies to the combined peak-to-peak signal and DC offset. Clipping occurs slightly above these levels.” This means that if the signal generator is impedance bridged with your circuit, don’t expect to generate signals outside of a ±10V range. If the signal generator is impedance matched with your circuit, don’t expect to generate signals outside of a ±5V range. This includes the DC offset in both cases. If your input impedance falls anywhere between 50 Ω and an open circuit (∞Ω), the maximum signal you can get from the signal generator will fall between ±5V and ±10V, respectively. Unless you really know what you are doing, do not use the signal generator on circuits that have an input impedance of less than 50 Ω. Similarly, do not choose an injection point in your circuit for the signal generator that has a DC voltage higher than what can be achieved with the DC offset knob. Only choose injection points where the DC voltage can be matched with the DC offset knob; otherwise, this can cause internal damage to the signal generator.