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Questions and Answers
What is the output voltage equation for a current-controlled voltage source (ICVS) if the transresistance is denoted by Rm and the input current is denoted by Ii?
What is the output voltage equation for a current-controlled voltage source (ICVS) if the transresistance is denoted by Rm and the input current is denoted by Ii?
Which type of source uses the value of the current at the output as Io = gm * Vi, where gm is the transconductance of the device?
Which type of source uses the value of the current at the output as Io = gm * Vi, where gm is the transconductance of the device?
In the context of amplifier signal modeling, what does the term 'input impedance' refer to?
In the context of amplifier signal modeling, what does the term 'input impedance' refer to?
What does the open circuit voltage gain of 50 signify in a certain amplifier characterized by Ri = 1500 ohms and Ro = 250 ohms?
What does the open circuit voltage gain of 50 signify in a certain amplifier characterized by Ri = 1500 ohms and Ro = 250 ohms?
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Which type of source has its output current defined as io = βii, where β represents the current gain and ii is the input current?
Which type of source has its output current defined as io = βii, where β represents the current gain and ii is the input current?
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Study Notes
Ideal Sources
- Ideal voltage sources and ideal current sources have values that are independent of any external loads connected to the devices.
- Ideal sources have unique characteristics that distinguish them from practical sources.
Ideal Voltage Source
- Generates a voltage Vs, which is independent of the current flowing through the source.
- Has zero internal resistance.
- The (+) and (-) terminals show the respective positive and negative terminals for the voltage.
Ideal Current Source
- Generates a current Is, which is independent of the voltage across the source.
- Has infinite internal resistance.
- The arrow indicates the assumed positive reference direction for the current.
Practical Sources
- Can be modeled by a combination of an ideal source and one or more passive circuit components.
- At relatively low frequencies, the passive component is often resistance.
- Can be represented using Thevenin and Norton models.
Thevenin and Norton Models
- Either model can be used to represent a practical source, provided that the only significant passive circuit parameter is resistance.
- Is = Vs/ Rs and Vs = Is Rs.
Controlled-Source Models
- There are four possible combinations of input-output control:
- Voltage-controlled voltage source.
- Voltage-controlled current source.
- Current-controlled voltage source.
- Current-controlled current source.
- A voltage-controlled voltage source is not affected by the output impedance of the source (sensor).
Ideal Amplifiers
- An ideal amplifier's gain is not affected by the output impedance of the source (sensor).
- An ideal amplifier can drive any load and supply any current.
- Real amplifiers are not ideal, but an op amp can come close, at least with regard to gain at low frequency.
Operational Amplifiers (Op Amps)
- Typical IC op amps have an open loop gain of 10^6 and a low frequency input impedance of about 10^12 ohms.
Amplifier Representation
- Amplifiers can be represented by a block diagram with input voltage signal Vi(t) and output voltage signal Vo(t).
- The quantity t refers to time, and the functions Vi(t) and Vo(t) represent the fact that both voltages are functions of time.
Voltage Gain
- Voltage gain (A) is the ratio of the output signal to the input signal.
- A = Vo(t) / Vi(t) and Vo(t) = A Vi(t).
- If the amplifier is not perfectly linear, the equation will no longer be correct.
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Description
Learn about ideal voltage sources and ideal current sources, including their characteristics and differences. Ideal voltage sources provide a constant voltage output independent of current, while ideal current sources provide a constant current output independent of voltage.
