When this Arizona-based ­microelectronics maker went public in 1993, it was a penny stock. Twenty-five years later, the company’s shares trade in the $60s and higher. The world’s seemingly bottomless appetite for ­computer chips has kept the business growing at a healthy clip, leading to nearly $4 billion in sales in its last fiscal year. Microchip Technology, known for its tiny, computer-like, ­microcontroller circuits, continues to expand by mak­ing big acquisitions, most recently picking up Microsemi, a California manufacturer, for $10 billion.