Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018
Cash flows from operating activities:
Net loss	$ (11,991)	$ (22,434)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,980	3,046
Share-based compensation expense	5,807	1,090
Loss on sale of fixed assets	0	76
Amortization of debt issuance costs	124	51
Change in preferred and common stock warrant liabilities	12,503	1,253
Net change in operating assets and liabilities:
Accounts receivable	(21,856)	(8,499)
Inventories	(30,013)	(9,627)
Prepaid expenses and other assets	(1,878)	(615)
Accounts payable	20,206	7,670
Accrued expenses and other current liabilities	2,768	3,573
Long-term liabilities	11	39
Net cash used in operating activities	(18,339)	(24,377)
Cash flows used in investing activities:
Purchases of property, plant and equipment	(9,515)	(18,250)
Proceeds from sale of fixed assets	307	104
Purchases of property, plant and equipment held for sale	(7,403)	0
Payment of security deposits	(542)	(59)
Net cash used in investing activities	(17,153)	(18,205)
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to the initial public offering, net of issuance costs	254,868	0
Proceeds from issuance of common stock pursuant to the secondary public offering, net of issuance costs	37,937	0
Proceeds from advance deposit for Series H preferred stock offering	0	25,000
Proceeds from Series G preferred stock offering, net of offering costs	0	1,347
Proceeds from bank term loan borrowing	0	20,000
Repayments on revolving credit line	0	(2,500)
Repayment on term loan	0	(1,000)
Proceeds from payoff of notes receivable for restricted stock purchase	0	951
Proceeds from revolving credit line	0	6,000
Proceeds from equipment loan borrowing	0	5,000
Repayment of Missouri Note	0	(1,450)
Payments of capital lease obligations	(31)	(143)
Proceeds from exercise of stock options	898	1,128
Payments of deferred offering costs	0	(492)
Payment for repurchase of common stock	0	(514)
Net cash provided by financing activities	293,672	53,327
Net increase in cash and cash equivalents	258,180	10,745
Cash and cash equivalents at the beginning of the period	54,271	39,035
Cash and cash equivalents at the end of the period	312,451	49,780
Cash paid during the period for:
Interest	2,261	356
Taxes	21	3
Non-cash investing and financing activities:
Capital lease obligations for the purchase of property, plant and equipment	0	85
Issuance of convertible preferred stock warrants in connection with debt	0	248
Non-cash additions to property, plant and equipment	1,280	730
Offering costs, accrued not yet paid	487	1,301
Non-cash additions to property, plant and equipment held for sale	1,019	0
Reclassification of warrant liability to additional paid-in capital in connection with the initial public offering	14,421	0
Conversion of convertible preferred stock to common stock upon initial public offering	$ 199,540	$ 0