Test

If Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle V_{in}} > 0.7V, then the current is amplified by the npn transistor.

If Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle V_{in}} < -0.7V, then the current is amplified by the pnp transistor.

Beware that there is a “dead band” when V_in is between 0.7V and -0.7V, because the voltage has not pass the cutoff voltage for either transistor. This is known as crossover distortion