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 Vb  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 vo is at the intersection of the tunnel diode curve and the resistor load line R  (blue).Since R &lt; r, if the two values are close in value the two resistances in series have a small negative value.  So a small increase in vi(green)   moves the load line right, resulting in a large decrease in current, causing a large increase in vo. The output isvo=rr−Rvi{\displaystyle v_{o}={\frac {r}{r-R}}v_{i}\,}
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