English: Graph of the load line of simple tunnel diode amplifier circuit (Tunnel diode amplifier.svg) showing how it amplifies a signal. The current from the bias battery V_b biases the diode into the center of its curve (black), where it has a negative differential resistance of r (red). The operating point and output voltage of the circuit v_o is at the intersection of the tunnel diode curve and the resistor load line R (blue).Since R < r, if the two values are close in value the two resistances in series have a small negative value. So a small increase in v_i (green) moves the load line right, resulting in a large decrease in current, causing a large increase in v_o. The output is

${\displaystyle v_{o}={\frac {r}{r-R}}v_{i}\,}$