Matched biasing transistors ensure automatic temperature compensation for common emitter amplifier

Art of Electronics 3rd ed. Figure 2.52 If both switches are on, the emitter degenerating resistors are not used (the gain is about 400) if both switches are off, the emitter degenerating resistors are used (the gain is about 50) This circuit uses matched transistor pair (on the same silicon). This ensures automatic temperature compensation.