Semiconductor Devices — MHT-CET Physics

Formulas (2)

• Conductors, Insulators and Semiconductors · Intrinsic semiconductor
  $$n_e = n_h = n_i$$
• n-type and p-type Doping · Mass-action law
  $$n_e\,n_h = n_i^2$$

Watch out for (2)

• A semiconductor's valence band is 'completely filled'
  → Conductors, Insulators and Semiconductors
• n-type means negatively charged
  → n-type and p-type Doping

Formulas (2)

• The Depletion Layer and Its Field · Barrier
  $$\vec E_{\text{junction}}: \; n \to p, \qquad V_n > V_p$$
• Forward and Reverse Bias · Bias rule
  $$V_p > V_n \Rightarrow \text{forward}, \qquad V_p < V_n \Rightarrow \text{reverse}$$

Watch out for (2)

• The p-side is at the higher potential
  → The Depletion Layer and Its Field
• Comparing the sizes of negative voltages
  → Forward and Reverse Bias

Formulas (2)

• Circuits With Diodes · Silicon diode in series
  $$I = \frac{V - 0.7}{R}$$
• Half-Wave and Full-Wave Rectifiers · Output frequency
  $$f_{\text{half}} = f, \qquad f_{\text{full}} = 2f$$

Watch out for (2)

• Including a reverse-biased branch
  → Circuits With Diodes
• Full-wave keeps the input frequency
  → Half-Wave and Full-Wave Rectifiers

Formulas (2)

• The Zener Regulator · Zener current
  $$I_Z = \frac{V_{\text{in}} - V_Z}{R_s} - \frac{V_Z}{R_L}$$
• LED, Photodiode and Solar Cell · Band gap and wavelength
  $$E_g = \frac{hc}{\lambda}, \qquad \lambda\,(\text{nm}) \approx \frac{1240}{E_g\,(\text{eV})}$$

Watch out for (2)

• Giving the Zener the whole series current
  → The Zener Regulator
• Detecting light in forward bias
  → LED, Photodiode and Solar Cell

Formulas (3)

• Current Ratios α and β · Current gains
  $$\alpha = \frac{I_C}{I_E}, \quad \beta = \frac{I_C}{I_B}, \quad \beta = \frac{\alpha}{1 - \alpha}$$
• The Common-Emitter Amplifier · CE amplifier
  $$A_V = \beta\,\frac{R_L}{R_{\text{in}}}, \qquad A_P = \beta\,A_V$$
• n-p-n and p-n-p Transistors · Currents
  $$I_E = I_B + I_C$$

Watch out for (3)

• Calling the collector fraction β
  → Current Ratios α and β
• Squaring β in the voltage gain
  → The Common-Emitter Amplifier
• Drawing the diodes pointing inward
  → n-p-n and p-n-p Transistors

Formulas (3)

• The Basic Gates and Their Truth Tables · NAND and NOR
  $$\text{NAND: } Y = \overline{A\cdot B}, \qquad \text{NOR: } Y = \overline{A + B}$$
• Which Single Gate Is a Combination Equal To? · De Morgan's laws
  $$\overline{A\cdot B} = \overline{A} + \overline{B}, \qquad \overline{A + B} = \overline{A}\cdot\overline{B}$$
• Output and Boolean Expression of a Circuit · Absorption
  $$A + \overline{A}B = A + B, \qquad A(A + B) = A$$

Watch out for (3)

• Reading one row and stopping
  → The Basic Gates and Their Truth Tables
• Missing the bubble
  → Which Single Gate Is a Combination Equal To?
• Trusting the pattern, not the gates
  → Output and Boolean Expression of a Circuit